From 09a52ed47bb26498c97a579ce1147861df696d84 Mon Sep 17 00:00:00 2001
From: Charles Harris <charlesr.harris@gmail.com>
Date: Thu, 28 Mar 2013 17:13:53 -0600
Subject: 2to3: Apply `imports` fixer.

The `imports` fixer deals with the standard packages that have been
renamed, removed, or methods that have moved.

cPickle      -- removed, use pickle
commands     -- removed, getoutput, getstatusoutput moved to subprocess
urlparse     -- removed, urlparse moved to urllib.parse
cStringIO    -- removed, use StringIO or io.StringIO
copy_reg     -- renamed copyreg
_winreg      -- renamed winreg
ConfigParser -- renamed configparser
__builtin__  -- renamed builtins

In the case of `cPickle`, it is imported as `pickle` when python < 3 and
performance may be a consideration, but otherwise plain old `pickle` is
used.

Dealing with `StringIO` is a bit tricky. There is an `io.StringIO`
function in the `io` module, available since Python 2.6, but it expects
unicode whereas `StringIO.StringIO` expects ascii. The Python 3
equivalent is then `io.BytesIO`. What I have done here is used BytesIO
for anything that is emulating a file for testing purposes. That is more
explicit than using a redefined StringIO as was done before we dropped
support for Python 2.4 and 2.5.

Closes #3180.
---
 numpy/lib/_datasource.py            |  12 +-
 numpy/lib/_iotools.py               |   6 +-
 numpy/lib/format.py                 |  11 +-
 numpy/lib/npyio.py                  |  18 +-
 numpy/lib/tests/test__datasource.py |  13 +-
 numpy/lib/tests/test__iotools.py    |  11 +-
 numpy/lib/tests/test_format.py      |  48 ++--
 numpy/lib/tests/test_io.py          | 461 +++++++++++++++++++-----------------
 numpy/lib/tests/test_regression.py  |   7 +-
 numpy/lib/tests/test_utils.py       |   6 +-
 numpy/lib/utils.py                  |   7 +-
 11 files changed, 314 insertions(+), 286 deletions(-)

(limited to 'numpy/lib')

diff --git a/numpy/lib/_datasource.py b/numpy/lib/_datasource.py
index db97c5507..9f0bb1ae8 100644
--- a/numpy/lib/_datasource.py
+++ b/numpy/lib/_datasource.py
@@ -36,6 +36,7 @@ from __future__ import division, absolute_import
 __docformat__ = "restructuredtext en"
 
 import os
+import sys
 from shutil import rmtree, copyfile, copyfileobj
 
 _open = open
@@ -252,7 +253,10 @@ class DataSource (object):
         """Test if path is a net location.  Tests the scheme and netloc."""
 
         # We do this here to reduce the 'import numpy' initial import time.
-        from urlparse import urlparse
+        if sys.version_info[0] >= 3:
+            from urllib.parse import urlparse
+        else:
+            from urlparse import urlparse
 
         # BUG : URLs require a scheme string ('http://') to be used.
         #       www.google.com will fail.
@@ -351,8 +355,10 @@ class DataSource (object):
 
         """
         # We do this here to reduce the 'import numpy' initial import time.
-        from urlparse import urlparse
-
+        if sys.version_info[0] >= 3:
+            from urllib.parse import urlparse
+        else:
+            from urlparse import urlparse
 
         # TODO:  This should be more robust.  Handles case where path includes
         #        the destpath, but not other sub-paths. Failing case:
diff --git a/numpy/lib/_iotools.py b/numpy/lib/_iotools.py
index 87ce9b01d..b8a01bafc 100644
--- a/numpy/lib/_iotools.py
+++ b/numpy/lib/_iotools.py
@@ -8,7 +8,11 @@ __docformat__ = "restructuredtext en"
 import sys
 import numpy as np
 import numpy.core.numeric as nx
-from __builtin__ import bool, int, long, float, complex, object, unicode, str
+
+if sys.version_info[0] >= 3:
+    from builtins import bool, int, long, float, complex, object, unicode, str
+else:
+    from __builtin__ import bool, int, long, float, complex, object, unicode, str
 
 from numpy.compat import asbytes, bytes, asbytes_nested
 
diff --git a/numpy/lib/format.py b/numpy/lib/format.py
index 21b0607e7..dedfabfd2 100644
--- a/numpy/lib/format.py
+++ b/numpy/lib/format.py
@@ -136,13 +136,16 @@ alternatives, is described fully in the "npy-format" NEP.
 """
 from __future__ import division, absolute_import
 
-import cPickle
-
 import numpy
 import sys
 from numpy.lib.utils import safe_eval
 from numpy.compat import asbytes, isfileobj
 
+if sys.version_info[0] >= 3:
+    import pickle
+else:
+    import cPickle as pickle
+
 MAGIC_PREFIX = asbytes('\x93NUMPY')
 MAGIC_LEN = len(MAGIC_PREFIX) + 2
 
@@ -399,7 +402,7 @@ def write_array(fp, array, version=(1,0)):
     if array.dtype.hasobject:
         # We contain Python objects so we cannot write out the data directly.
         # Instead, we will pickle it out with version 2 of the pickle protocol.
-        cPickle.dump(array, fp, protocol=2)
+        pickle.dump(array, fp, protocol=2)
     elif array.flags.f_contiguous and not array.flags.c_contiguous:
         if isfileobj(fp):
             array.T.tofile(fp)
@@ -447,7 +450,7 @@ def read_array(fp):
     # Now read the actual data.
     if dtype.hasobject:
         # The array contained Python objects. We need to unpickle the data.
-        array = cPickle.load(fp)
+        array = pickle.load(fp)
     else:
         if isfileobj(fp):
             # We can use the fast fromfile() function.
diff --git a/numpy/lib/npyio.py b/numpy/lib/npyio.py
index 065a3ba46..eb4ffd4ce 100644
--- a/numpy/lib/npyio.py
+++ b/numpy/lib/npyio.py
@@ -1,9 +1,5 @@
 from __future__ import division, absolute_import
 
-__all__ = ['savetxt', 'loadtxt', 'genfromtxt', 'ndfromtxt', 'mafromtxt',
-           'recfromtxt', 'recfromcsv', 'load', 'loads', 'save', 'savez',
-           'savez_compressed', 'packbits', 'unpackbits', 'fromregex', 'DataSource']
-
 import numpy as np
 from . import format
 import sys
@@ -15,7 +11,6 @@ import warnings
 import weakref
 from operator import itemgetter
 
-from cPickle import load as _cload, loads
 from ._datasource import DataSource
 from ._compiled_base import packbits, unpackbits
 
@@ -25,11 +20,18 @@ from ._iotools import LineSplitter, NameValidator, StringConverter, \
                      easy_dtype, _bytes_to_name
 
 from numpy.compat import asbytes, asstr, asbytes_nested, bytes
+from io import BytesIO
 
 if sys.version_info[0] >= 3:
-    from io import BytesIO
+    import pickle
 else:
-    from cStringIO import StringIO as BytesIO
+    import cPickle as pickle
+
+loads = pickle.loads
+
+__all__ = ['savetxt', 'loadtxt', 'genfromtxt', 'ndfromtxt', 'mafromtxt',
+           'recfromtxt', 'recfromcsv', 'load', 'loads', 'save', 'savez',
+           'savez_compressed', 'packbits', 'unpackbits', 'fromregex', 'DataSource']
 
 _string_like = _is_string_like
 
@@ -380,7 +382,7 @@ def load(file, mmap_mode=None):
                 return format.read_array(fid)
         else:  # Try a pickle
             try:
-                return _cload(fid)
+                return pickle.load(fid)
             except:
                 raise IOError(
                     "Failed to interpret file %s as a pickle" % repr(file))
diff --git a/numpy/lib/tests/test__datasource.py b/numpy/lib/tests/test__datasource.py
index e784e4296..ccd7405fe 100644
--- a/numpy/lib/tests/test__datasource.py
+++ b/numpy/lib/tests/test__datasource.py
@@ -1,17 +1,20 @@
 from __future__ import division, absolute_import
 
 import os
+import urllib2
+import sys
+import numpy.lib._datasource as datasource
 from tempfile import mkdtemp, mkstemp, NamedTemporaryFile
 from shutil import rmtree
-from urlparse import urlparse
 from urllib2 import URLError
-import urllib2
-
+from numpy.compat import asbytes
 from numpy.testing import *
 
-from numpy.compat import asbytes
 
-import numpy.lib._datasource as datasource
+if sys.version_info[0] >= 3:
+    from urllib.parse import urlparse
+else:
+    from urlparse import urlparse
 
 def urlopen_stub(url, data=None):
     '''Stub to replace urlopen for testing.'''
diff --git a/numpy/lib/tests/test__iotools.py b/numpy/lib/tests/test__iotools.py
index ebb01ad3a..1cd9a25da 100644
--- a/numpy/lib/tests/test__iotools.py
+++ b/numpy/lib/tests/test__iotools.py
@@ -1,22 +1,13 @@
 from __future__ import division, absolute_import
 
 import sys
-
-if sys.version_info[0] >= 3:
-    from io import BytesIO
-    def StringIO(s=""):
-        return BytesIO(asbytes(s))
-else:
-    from StringIO import StringIO
-
-from datetime import date
 import time
+from datetime import date
 
 import numpy as np
 from numpy.lib._iotools import LineSplitter, NameValidator, StringConverter, \
                                has_nested_fields, easy_dtype, flatten_dtype
 from numpy.testing import *
-
 from numpy.compat import asbytes, asbytes_nested
 
 class TestLineSplitter(TestCase):
diff --git a/numpy/lib/tests/test_format.py b/numpy/lib/tests/test_format.py
index 5c07da1c3..aae3b1ba8 100644
--- a/numpy/lib/tests/test_format.py
+++ b/numpy/lib/tests/test_format.py
@@ -5,10 +5,7 @@ r''' Test the .npy file format.
 Set up:
 
     >>> import sys
-    >>> if sys.version_info[0] >= 3:
-    ...     from io import BytesIO as StringIO
-    ... else:
-    ...     from cStringIO import StringIO
+    >>> from io import BytesIO
     >>> from numpy.lib import format
     >>>
     >>> scalars = [
@@ -101,19 +98,19 @@ Test the magic string writing.
 
 Test the magic string reading.
 
-    >>> format.read_magic(StringIO(format.magic(1, 0)))
+    >>> format.read_magic(BytesIO(format.magic(1, 0)))
     (1, 0)
-    >>> format.read_magic(StringIO(format.magic(0, 0)))
+    >>> format.read_magic(BytesIO(format.magic(0, 0)))
     (0, 0)
-    >>> format.read_magic(StringIO(format.magic(255, 255)))
+    >>> format.read_magic(BytesIO(format.magic(255, 255)))
     (255, 255)
-    >>> format.read_magic(StringIO(format.magic(2, 5)))
+    >>> format.read_magic(BytesIO(format.magic(2, 5)))
     (2, 5)
 
 Test the header writing.
 
     >>> for arr in basic_arrays + record_arrays:
-    ...     f = StringIO()
+    ...     f = BytesIO()
     ...     format.write_array_header_1_0(f, arr)   # XXX: arr is not a dict, items gets called on it
     ...     print repr(f.getvalue())
     ...
@@ -279,22 +276,15 @@ Test the header writing.
     "\x16\x02{'descr': [('x', '>i4', (2,)),\n           ('Info',\n            [('value', '>c16'),\n             ('y2', '>f8'),\n             ('Info2',\n              [('name', '|S2'),\n               ('value', '>c16', (2,)),\n               ('y3', '>f8', (2,)),\n               ('z3', '>u4', (2,))]),\n             ('name', '|S2'),\n             ('z2', '|b1')]),\n           ('color', '|S2'),\n           ('info', [('Name', '>U8'), ('Value', '>c16')]),\n           ('y', '>f8', (2, 2)),\n           ('z', '|u1')],\n 'fortran_order': False,\n 'shape': (2,)}      \n"
 '''
 
-
 import sys
 import os
 import shutil
 import tempfile
-
-if sys.version_info[0] >= 3:
-    from io import BytesIO as StringIO
-else:
-    from cStringIO import StringIO
+from io import BytesIO
 
 import numpy as np
 from numpy.testing import *
-
 from numpy.lib import format
-
 from numpy.compat import asbytes, asbytes_nested
 
 
@@ -416,9 +406,9 @@ record_arrays = [
 ]
 
 def roundtrip(arr):
-    f = StringIO()
+    f = BytesIO()
     format.write_array(f, arr)
-    f2 = StringIO(f.getvalue())
+    f2 = BytesIO(f.getvalue())
     arr2 = format.read_array(f2)
     return arr2
 
@@ -469,7 +459,7 @@ def test_memmap_roundtrip():
 
 
 def test_write_version_1_0():
-    f = StringIO()
+    f = BytesIO()
     arr = np.arange(1)
     # These should pass.
     format.write_array(f, arr, version=(1, 0))
@@ -513,12 +503,12 @@ malformed_magic = asbytes_nested([
 
 def test_read_magic_bad_magic():
     for magic in malformed_magic:
-        f = StringIO(magic)
+        f = BytesIO(magic)
         yield raises(ValueError)(format.read_magic), f
 
 def test_read_version_1_0_bad_magic():
     for magic in bad_version_magic + malformed_magic:
-        f = StringIO(magic)
+        f = BytesIO(magic)
         yield raises(ValueError)(format.read_array), f
 
 def test_bad_magic_args():
@@ -528,29 +518,29 @@ def test_bad_magic_args():
     assert_raises(ValueError, format.magic, 1, 256)
 
 def test_large_header():
-    s = StringIO()
+    s = BytesIO()
     d = {'a':1,'b':2}
     format.write_array_header_1_0(s,d)
 
-    s = StringIO()
+    s = BytesIO()
     d = {'a':1,'b':2,'c':'x'*256*256}
     assert_raises(ValueError, format.write_array_header_1_0, s, d)
 
 def test_bad_header():
     # header of length less than 2 should fail
-    s = StringIO()
+    s = BytesIO()
     assert_raises(ValueError, format.read_array_header_1_0, s)
-    s = StringIO(asbytes('1'))
+    s = BytesIO(asbytes('1'))
     assert_raises(ValueError, format.read_array_header_1_0, s)
 
     # header shorter than indicated size should fail
-    s = StringIO(asbytes('\x01\x00'))
+    s = BytesIO(asbytes('\x01\x00'))
     assert_raises(ValueError, format.read_array_header_1_0, s)
 
     # headers without the exact keys required should fail
     d = {"shape":(1,2),
          "descr":"x"}
-    s = StringIO()
+    s = BytesIO()
     format.write_array_header_1_0(s,d)
     assert_raises(ValueError, format.read_array_header_1_0, s)
 
@@ -558,7 +548,7 @@ def test_bad_header():
          "fortran_order":False,
          "descr":"x",
          "extrakey":-1}
-    s = StringIO()
+    s = BytesIO()
     format.write_array_header_1_0(s,d)
     assert_raises(ValueError, format.read_array_header_1_0, s)
 
diff --git a/numpy/lib/tests/test_io.py b/numpy/lib/tests/test_io.py
index ab990976e..6b5173890 100644
--- a/numpy/lib/tests/test_io.py
+++ b/numpy/lib/tests/test_io.py
@@ -4,31 +4,43 @@ import sys
 import gzip
 import os
 import threading
-from tempfile import mkstemp, NamedTemporaryFile
 import time
-from datetime import datetime
 import warnings
 import gc
+from tempfile import mkstemp, NamedTemporaryFile
+from io import BytesIO
+from datetime import datetime
 from numpy.testing.utils import WarningManager
 
 import numpy as np
 import numpy.ma as ma
 from numpy.lib._iotools import ConverterError, ConverterLockError, \
                                ConversionWarning
-from numpy.compat import asbytes, asbytes_nested, bytes
-
+from numpy.compat import asbytes, asbytes_nested, bytes, asstr
 from nose import SkipTest
 from numpy.ma.testutils import (TestCase, assert_equal, assert_array_equal,
     assert_raises, run_module_suite)
 from numpy.testing import assert_warns, assert_, build_err_msg
 
-if sys.version_info[0] >= 3:
-    from io import BytesIO
-    def StringIO(s=""):
-        return BytesIO(asbytes(s))
-else:
-    from StringIO import StringIO
-    BytesIO = StringIO
+
+class TextIO(BytesIO):
+    """Helper IO class.
+
+    Writes encode strings to bytes if needed, reads return bytes.
+    This makes it easier to emulate files opened in binary mode
+    without needing to explicitly convert strings to bytes in
+    setting up the test data.
+
+    """
+    def __init__(self, s=""):
+        BytesIO.__init__(self, asbytes(s))
+
+    def write(self, s):
+        BytesIO.write(self, asbytes(s))
+
+    def writelines(self, lines):
+        BytesIO.writelines(self, [asbytes(s) for s in lines])
+
 
 MAJVER, MINVER = sys.version_info[:2]
 
@@ -73,7 +85,7 @@ class RoundtripTest(object):
                 target_file = NamedTemporaryFile()
             load_file = target_file.name
         else:
-            target_file = StringIO()
+            target_file = BytesIO()
             load_file = target_file
 
         arr = args
@@ -135,7 +147,7 @@ class TestSavezLoad(RoundtripTest, TestCase):
     def test_named_arrays(self):
         a = np.array([[1, 2], [3, 4]], float)
         b = np.array([[1 + 2j, 2 + 7j], [3 - 6j, 4 + 12j]], complex)
-        c = StringIO()
+        c = BytesIO()
         np.savez(c, file_a=a, file_b=b)
         c.seek(0)
         l = np.load(c)
@@ -228,95 +240,94 @@ class TestSaveTxt(TestCase):
     def test_array(self):
         a = np.array([[1, 2], [3, 4]], float)
         fmt = "%.18e"
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt=fmt)
         c.seek(0)
         assert_equal(c.readlines(),
-                     asbytes_nested(
-            [(fmt + ' ' + fmt + '\n') % (1, 2),
-             (fmt + ' ' + fmt + '\n') % (3, 4)]))
+            [asbytes((fmt + ' ' + fmt + '\n') % (1, 2)),
+             asbytes((fmt + ' ' + fmt + '\n') % (3, 4))])
 
         a = np.array([[1, 2], [3, 4]], int)
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt='%d')
         c.seek(0)
-        assert_equal(c.readlines(), asbytes_nested(['1 2\n', '3 4\n']))
+        assert_equal(c.readlines(), [b'1 2\n', b'3 4\n'])
 
     def test_1D(self):
         a = np.array([1, 2, 3, 4], int)
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt='%d')
         c.seek(0)
         lines = c.readlines()
-        assert_equal(lines, asbytes_nested(['1\n', '2\n', '3\n', '4\n']))
+        assert_equal(lines, [b'1\n', b'2\n', b'3\n', b'4\n'])
 
     def test_record(self):
         a = np.array([(1, 2), (3, 4)], dtype=[('x', 'i4'), ('y', 'i4')])
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt='%d')
         c.seek(0)
-        assert_equal(c.readlines(), asbytes_nested(['1 2\n', '3 4\n']))
+        assert_equal(c.readlines(), [b'1 2\n', b'3 4\n'])
 
     def test_delimiter(self):
         a = np.array([[1., 2.], [3., 4.]])
-        c = StringIO()
-        np.savetxt(c, a, delimiter=asbytes(','), fmt='%d')
+        c = BytesIO()
+        np.savetxt(c, a, delimiter=',', fmt='%d')
         c.seek(0)
-        assert_equal(c.readlines(), asbytes_nested(['1,2\n', '3,4\n']))
+        assert_equal(c.readlines(), [b'1,2\n', b'3,4\n'])
 
     def test_format(self):
         a = np.array([(1, 2), (3, 4)])
-        c = StringIO()
+        c = BytesIO()
         # Sequence of formats
         np.savetxt(c, a, fmt=['%02d', '%3.1f'])
         c.seek(0)
-        assert_equal(c.readlines(), asbytes_nested(['01 2.0\n', '03 4.0\n']))
+        assert_equal(c.readlines(), [b'01 2.0\n', b'03 4.0\n'])
 
         # A single multiformat string
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt='%02d : %3.1f')
         c.seek(0)
         lines = c.readlines()
-        assert_equal(lines, asbytes_nested(['01 : 2.0\n', '03 : 4.0\n']))
+        assert_equal(lines, [b'01 : 2.0\n', b'03 : 4.0\n'])
 
         # Specify delimiter, should be overiden
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt='%02d : %3.1f', delimiter=',')
         c.seek(0)
         lines = c.readlines()
-        assert_equal(lines, asbytes_nested(['01 : 2.0\n', '03 : 4.0\n']))
+        assert_equal(lines, [b'01 : 2.0\n', b'03 : 4.0\n'])
 
     def test_header_footer(self):
         """
         Test the functionality of the header and footer keyword argument.
         """
-        c = StringIO()
+        c = BytesIO()
         a = np.array([(1, 2), (3, 4)], dtype=np.int)
         test_header_footer = 'Test header / footer'
         # Test the header keyword argument
         np.savetxt(c, a, fmt='%1d', header=test_header_footer)
         c.seek(0)
         assert_equal(c.read(),
-                asbytes('# ' + test_header_footer +'\n1 2\n3 4\n' ))
+                asbytes('# ' + test_header_footer + '\n1 2\n3 4\n'))
         # Test the footer keyword argument
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt='%1d', footer=test_header_footer)
         c.seek(0)
         assert_equal(c.read(),
                 asbytes('1 2\n3 4\n# ' + test_header_footer + '\n'))
         # Test the commentstr keyword argument used on the header
-        c = StringIO()
+        c = BytesIO()
         commentstr = '% '
-        np.savetxt(c, a, fmt='%1d', header=test_header_footer,
-                comments=commentstr)
+        np.savetxt(c, a, fmt='%1d',
+                header=test_header_footer, comments=commentstr)
         c.seek(0)
         assert_equal(c.read(),
                 asbytes(commentstr + test_header_footer + '\n' + '1 2\n3 4\n'))
         # Test the commentstr keyword argument used on the footer
-        c = StringIO()
+        c = BytesIO()
         commentstr = '% '
-        np.savetxt(c, a, fmt='%1d', footer=test_header_footer,
-                comments=commentstr)
+        np.savetxt(c, a, fmt='%1d',
+                footer=test_header_footer, comments=commentstr)
         c.seek(0)
         assert_equal(c.read(),
                 asbytes('1 2\n3 4\n' + commentstr + test_header_footer + '\n'))
@@ -340,29 +351,29 @@ class TestSaveTxt(TestCase):
         im = np.e
         a[:] = re + 1.0j * im
         # One format only
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt=' %+.3e')
         c.seek(0)
         lines = c.readlines()
-        _assert_floatstr_lines_equal(lines, asbytes_nested([
-            ' ( +3.142e+00+ +2.718e+00j)  ( +3.142e+00+ +2.718e+00j)\n',
-            ' ( +3.142e+00+ +2.718e+00j)  ( +3.142e+00+ +2.718e+00j)\n']))
+        _assert_floatstr_lines_equal(lines,
+                [b' ( +3.142e+00+ +2.718e+00j)  ( +3.142e+00+ +2.718e+00j)\n',
+                 b' ( +3.142e+00+ +2.718e+00j)  ( +3.142e+00+ +2.718e+00j)\n'])
         # One format for each real and imaginary part
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt='  %+.3e' * 2 * ncols)
         c.seek(0)
         lines = c.readlines()
-        _assert_floatstr_lines_equal(lines, asbytes_nested([
-            '  +3.142e+00  +2.718e+00  +3.142e+00  +2.718e+00\n',
-            '  +3.142e+00  +2.718e+00  +3.142e+00  +2.718e+00\n']))
+        _assert_floatstr_lines_equal(lines,
+                [b'  +3.142e+00  +2.718e+00  +3.142e+00  +2.718e+00\n',
+                 b'  +3.142e+00  +2.718e+00  +3.142e+00  +2.718e+00\n'])
         # One format for each complex number
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a, fmt=['(%.3e%+.3ej)'] * ncols)
         c.seek(0)
         lines = c.readlines()
-        _assert_floatstr_lines_equal(lines, asbytes_nested([
-            '(3.142e+00+2.718e+00j) (3.142e+00+2.718e+00j)\n',
-            '(3.142e+00+2.718e+00j) (3.142e+00+2.718e+00j)\n']))
+        _assert_floatstr_lines_equal(lines,
+                [b'(3.142e+00+2.718e+00j) (3.142e+00+2.718e+00j)\n',
+                 b'(3.142e+00+2.718e+00j) (3.142e+00+2.718e+00j)\n'])
 
 
 def _assert_floatstr_lines_equal(actual_lines, expected_lines):
@@ -387,15 +398,15 @@ def _assert_floatstr_lines_equal(actual_lines, expected_lines):
 
 class TestLoadTxt(TestCase):
     def test_record(self):
-        c = StringIO()
-        c.write(asbytes('1 2\n3 4'))
+        c = TextIO()
+        c.write('1 2\n3 4')
         c.seek(0)
         x = np.loadtxt(c, dtype=[('x', np.int32), ('y', np.int32)])
         a = np.array([(1, 2), (3, 4)], dtype=[('x', 'i4'), ('y', 'i4')])
         assert_array_equal(x, a)
 
-        d = StringIO()
-        d.write(asbytes('M 64.0 75.0\nF 25.0 60.0'))
+        d = TextIO()
+        d.write('M 64.0 75.0\nF 25.0 60.0')
         d.seek(0)
         mydescriptor = {'names': ('gender', 'age', 'weight'),
                         'formats': ('S1',
@@ -406,8 +417,8 @@ class TestLoadTxt(TestCase):
         assert_array_equal(y, b)
 
     def test_array(self):
-        c = StringIO()
-        c.write(asbytes('1 2\n3 4'))
+        c = TextIO()
+        c.write('1 2\n3 4')
 
         c.seek(0)
         x = np.loadtxt(c, dtype=int)
@@ -420,23 +431,23 @@ class TestLoadTxt(TestCase):
         assert_array_equal(x, a)
 
     def test_1D(self):
-        c = StringIO()
-        c.write(asbytes('1\n2\n3\n4\n'))
+        c = TextIO()
+        c.write('1\n2\n3\n4\n')
         c.seek(0)
         x = np.loadtxt(c, dtype=int)
         a = np.array([1, 2, 3, 4], int)
         assert_array_equal(x, a)
 
-        c = StringIO()
-        c.write(asbytes('1,2,3,4\n'))
+        c = TextIO()
+        c.write('1,2,3,4\n')
         c.seek(0)
         x = np.loadtxt(c, dtype=int, delimiter=',')
         a = np.array([1, 2, 3, 4], int)
         assert_array_equal(x, a)
 
     def test_missing(self):
-        c = StringIO()
-        c.write(asbytes('1,2,3,,5\n'))
+        c = TextIO()
+        c.write('1,2,3,,5\n')
         c.seek(0)
         x = np.loadtxt(c, dtype=int, delimiter=',', \
             converters={3:lambda s: int(s or - 999)})
@@ -444,8 +455,8 @@ class TestLoadTxt(TestCase):
         assert_array_equal(x, a)
 
     def test_converters_with_usecols(self):
-        c = StringIO()
-        c.write(asbytes('1,2,3,,5\n6,7,8,9,10\n'))
+        c = TextIO()
+        c.write('1,2,3,,5\n6,7,8,9,10\n')
         c.seek(0)
         x = np.loadtxt(c, dtype=int, delimiter=',', \
             converters={3:lambda s: int(s or - 999)}, \
@@ -454,8 +465,8 @@ class TestLoadTxt(TestCase):
         assert_array_equal(x, a)
 
     def test_comments(self):
-        c = StringIO()
-        c.write(asbytes('# comment\n1,2,3,5\n'))
+        c = TextIO()
+        c.write('# comment\n1,2,3,5\n')
         c.seek(0)
         x = np.loadtxt(c, dtype=int, delimiter=',', \
             comments='#')
@@ -463,16 +474,16 @@ class TestLoadTxt(TestCase):
         assert_array_equal(x, a)
 
     def test_skiprows(self):
-        c = StringIO()
-        c.write(asbytes('comment\n1,2,3,5\n'))
+        c = TextIO()
+        c.write('comment\n1,2,3,5\n')
         c.seek(0)
         x = np.loadtxt(c, dtype=int, delimiter=',', \
             skiprows=1)
         a = np.array([1, 2, 3, 5], int)
         assert_array_equal(x, a)
 
-        c = StringIO()
-        c.write(asbytes('# comment\n1,2,3,5\n'))
+        c = TextIO()
+        c.write('# comment\n1,2,3,5\n')
         c.seek(0)
         x = np.loadtxt(c, dtype=int, delimiter=',', \
             skiprows=1)
@@ -481,14 +492,14 @@ class TestLoadTxt(TestCase):
 
     def test_usecols(self):
         a = np.array([[1, 2], [3, 4]], float)
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a)
         c.seek(0)
         x = np.loadtxt(c, dtype=float, usecols=(1,))
         assert_array_equal(x, a[:, 1])
 
         a = np.array([[1, 2, 3], [3, 4, 5]], float)
-        c = StringIO()
+        c = BytesIO()
         np.savetxt(c, a)
         c.seek(0)
         x = np.loadtxt(c, dtype=float, usecols=(1, 2))
@@ -503,16 +514,16 @@ class TestLoadTxt(TestCase):
         data = '''JOE 70.1 25.3
                 BOB 60.5 27.9
                 '''
-        c = StringIO(data)
+        c = TextIO(data)
         names = ['stid', 'temp']
         dtypes = ['S4', 'f8']
         arr = np.loadtxt(c, usecols=(0, 2), dtype=zip(names, dtypes))
-        assert_equal(arr['stid'], asbytes_nested(["JOE", "BOB"]))
+        assert_equal(arr['stid'], [b"JOE", b"BOB"])
         assert_equal(arr['temp'], [25.3, 27.9])
 
     def test_fancy_dtype(self):
-        c = StringIO()
-        c.write(asbytes('1,2,3.0\n4,5,6.0\n'))
+        c = TextIO()
+        c.write('1,2,3.0\n4,5,6.0\n')
         c.seek(0)
         dt = np.dtype([('x', int), ('y', [('t', int), ('s', float)])])
         x = np.loadtxt(c, dtype=dt, delimiter=',')
@@ -520,7 +531,7 @@ class TestLoadTxt(TestCase):
         assert_array_equal(x, a)
 
     def test_shaped_dtype(self):
-        c = StringIO("aaaa  1.0  8.0  1 2 3 4 5 6")
+        c = TextIO("aaaa  1.0  8.0  1 2 3 4 5 6")
         dt = np.dtype([('name', 'S4'), ('x', float), ('y', float),
                        ('block', int, (2, 3))])
         x = np.loadtxt(c, dtype=dt)
@@ -529,7 +540,7 @@ class TestLoadTxt(TestCase):
         assert_array_equal(x, a)
 
     def test_3d_shaped_dtype(self):
-        c = StringIO("aaaa  1.0  8.0  1 2 3 4 5 6 7 8 9 10 11 12")
+        c = TextIO("aaaa  1.0  8.0  1 2 3 4 5 6 7 8 9 10 11 12")
         dt = np.dtype([('name', 'S4'), ('x', float), ('y', float),
                        ('block', int, (2, 2, 3))])
         x = np.loadtxt(c, dtype=dt)
@@ -543,7 +554,7 @@ class TestLoadTxt(TestCase):
         try:
             warnings.filterwarnings("ignore",
                     message="loadtxt: Empty input file:")
-            c = StringIO()
+            c = TextIO()
             x = np.loadtxt(c)
             assert_equal(x.shape, (0,))
             x = np.loadtxt(c, dtype=np.int64)
@@ -554,8 +565,8 @@ class TestLoadTxt(TestCase):
 
 
     def test_unused_converter(self):
-        c = StringIO()
-        c.writelines([asbytes('1 21\n'), asbytes('3 42\n')])
+        c = TextIO()
+        c.writelines(['1 21\n', '3 42\n'])
         c.seek(0)
         data = np.loadtxt(c, usecols=(1,),
                           converters={0: lambda s: int(s, 16)})
@@ -570,12 +581,12 @@ class TestLoadTxt(TestCase):
         "Test using an explicit dtype with an object"
         from datetime import date
         import time
-        data = asbytes(""" 1; 2001-01-01
-                           2; 2002-01-31 """)
+        data = """ 1; 2001-01-01
+                   2; 2002-01-31 """
         ndtype = [('idx', int), ('code', np.object)]
         func = lambda s: strptime(s.strip(), "%Y-%m-%d")
         converters = {1: func}
-        test = np.loadtxt(StringIO(data), delimiter=";", dtype=ndtype,
+        test = np.loadtxt(TextIO(data), delimiter=";", dtype=ndtype,
                              converters=converters)
         control = np.array([(1, datetime(2001, 1, 1)), (2, datetime(2002, 1, 31))],
                            dtype=ndtype)
@@ -583,23 +594,23 @@ class TestLoadTxt(TestCase):
 
     def test_uint64_type(self):
         tgt = (9223372043271415339, 9223372043271415853)
-        c = StringIO()
-        c.write(asbytes("%s %s" % tgt))
+        c = TextIO()
+        c.write("%s %s" % tgt)
         c.seek(0)
         res = np.loadtxt(c, dtype=np.uint64)
         assert_equal(res, tgt)
 
     def test_int64_type(self):
         tgt = (-9223372036854775807, 9223372036854775807)
-        c = StringIO()
-        c.write(asbytes("%s %s" % tgt))
+        c = TextIO()
+        c.write("%s %s" % tgt)
         c.seek(0)
         res = np.loadtxt(c, dtype=np.int64)
         assert_equal(res, tgt)
 
     def test_universal_newline(self):
         f, name = mkstemp()
-        os.write(f, asbytes('1 21\r3 42\r'))
+        os.write(f, b'1 21\r3 42\r')
         os.close(f)
 
         try:
@@ -609,29 +620,29 @@ class TestLoadTxt(TestCase):
             os.unlink(name)
 
     def test_empty_field_after_tab(self):
-        c = StringIO()
-        c.write(asbytes('1 \t2 \t3\tstart \n4\t5\t6\t  \n7\t8\t9.5\t'))
+        c = TextIO()
+        c.write('1 \t2 \t3\tstart \n4\t5\t6\t  \n7\t8\t9.5\t')
         c.seek(0)
         dt = { 'names': ('x', 'y', 'z', 'comment'),
                'formats': ('<i4', '<i4', '<f4', '|S8')}
         x = np.loadtxt(c, dtype=dt, delimiter='\t')
-        a = np.array([asbytes('start '), asbytes('  '), asbytes('')])
+        a = np.array([b'start ', b'  ', b''])
         assert_array_equal(x['comment'], a)
 
     def test_structure_unpack(self):
-        txt = StringIO(asbytes("M 21 72\nF 35 58"))
+        txt = TextIO("M 21 72\nF 35 58")
         dt = { 'names': ('a', 'b', 'c'), 'formats': ('|S1', '<i4', '<f4')}
         a, b, c = np.loadtxt(txt, dtype=dt, unpack=True)
         assert_(a.dtype.str == '|S1')
         assert_(b.dtype.str == '<i4')
         assert_(c.dtype.str == '<f4')
-        assert_array_equal(a, np.array([asbytes('M'), asbytes('F')]))
+        assert_array_equal(a, np.array([b'M', b'F']))
         assert_array_equal(b, np.array([21, 35]))
         assert_array_equal(c, np.array([ 72.,  58.]))
 
     def test_ndmin_keyword(self):
-        c = StringIO()
-        c.write(asbytes('1,2,3\n4,5,6'))
+        c = TextIO()
+        c.write('1,2,3\n4,5,6')
         c.seek(0)
         assert_raises(ValueError, np.loadtxt, c, ndmin=3)
         c.seek(0)
@@ -640,8 +651,9 @@ class TestLoadTxt(TestCase):
         x = np.loadtxt(c, dtype=int, delimiter=',', ndmin=1)
         a = np.array([[1, 2, 3], [4, 5, 6]])
         assert_array_equal(x, a)
-        d = StringIO()
-        d.write(asbytes('0,1,2'))
+
+        d = TextIO()
+        d.write('0,1,2')
         d.seek(0)
         x = np.loadtxt(d, dtype=int, delimiter=',', ndmin=2)
         assert_(x.shape == (1, 3))
@@ -651,8 +663,9 @@ class TestLoadTxt(TestCase):
         d.seek(0)
         x = np.loadtxt(d, dtype=int, delimiter=',', ndmin=0)
         assert_(x.shape == (3,))
-        e = StringIO()
-        e.write(asbytes('0\n1\n2'))
+
+        e = TextIO()
+        e.write('0\n1\n2')
         e.seek(0)
         x = np.loadtxt(e, dtype=int, delimiter=',', ndmin=2)
         assert_(x.shape == (3, 1))
@@ -669,7 +682,7 @@ class TestLoadTxt(TestCase):
         try:
             warnings.filterwarnings("ignore",
                     message="loadtxt: Empty input file:")
-            f = StringIO()
+            f = TextIO()
             assert_(np.loadtxt(f, ndmin=2).shape == (0, 1,))
             assert_(np.loadtxt(f, ndmin=1).shape == (0,))
         finally:
@@ -678,15 +691,16 @@ class TestLoadTxt(TestCase):
     def test_generator_source(self):
         def count():
             for i in range(10):
-                yield asbytes("%d" % i)
+                yield "%d" % i
 
         res = np.loadtxt(count())
         assert_array_equal(res, np.arange(10))
 
 class Testfromregex(TestCase):
+    # np.fromregex expects files opened in binary mode.
     def test_record(self):
-        c = StringIO()
-        c.write(asbytes('1.312 foo\n1.534 bar\n4.444 qux'))
+        c = TextIO()
+        c.write('1.312 foo\n1.534 bar\n4.444 qux')
         c.seek(0)
 
         dt = [('num', np.float64), ('val', 'S3')]
@@ -696,8 +710,8 @@ class Testfromregex(TestCase):
         assert_array_equal(x, a)
 
     def test_record_2(self):
-        c = StringIO()
-        c.write(asbytes('1312 foo\n1534 bar\n4444 qux'))
+        c = TextIO()
+        c.write('1312 foo\n1534 bar\n4444 qux')
         c.seek(0)
 
         dt = [('num', np.int32), ('val', 'S3')]
@@ -707,8 +721,8 @@ class Testfromregex(TestCase):
         assert_array_equal(x, a)
 
     def test_record_3(self):
-        c = StringIO()
-        c.write(asbytes('1312 foo\n1534 bar\n4444 qux'))
+        c = TextIO()
+        c.write('1312 foo\n1534 bar\n4444 qux')
         c.seek(0)
 
         dt = [('num', np.float64)]
@@ -724,13 +738,13 @@ class TestFromTxt(TestCase):
     #
     def test_record(self):
         "Test w/ explicit dtype"
-        data = StringIO(asbytes('1 2\n3 4'))
+        data = TextIO('1 2\n3 4')
 #        data.seek(0)
         test = np.ndfromtxt(data, dtype=[('x', np.int32), ('y', np.int32)])
         control = np.array([(1, 2), (3, 4)], dtype=[('x', 'i4'), ('y', 'i4')])
         assert_equal(test, control)
         #
-        data = StringIO('M 64.0 75.0\nF 25.0 60.0')
+        data = TextIO('M 64.0 75.0\nF 25.0 60.0')
 #        data.seek(0)
         descriptor = {'names': ('gender', 'age', 'weight'),
                       'formats': ('S1', 'i4', 'f4')}
@@ -741,7 +755,7 @@ class TestFromTxt(TestCase):
 
     def test_array(self):
         "Test outputing a standard ndarray"
-        data = StringIO('1 2\n3 4')
+        data = TextIO('1 2\n3 4')
         control = np.array([[1, 2], [3, 4]], dtype=int)
         test = np.ndfromtxt(data, dtype=int)
         assert_array_equal(test, control)
@@ -755,36 +769,36 @@ class TestFromTxt(TestCase):
         "Test squeezing to 1D"
         control = np.array([1, 2, 3, 4], int)
         #
-        data = StringIO('1\n2\n3\n4\n')
+        data = TextIO('1\n2\n3\n4\n')
         test = np.ndfromtxt(data, dtype=int)
         assert_array_equal(test, control)
         #
-        data = StringIO('1,2,3,4\n')
-        test = np.ndfromtxt(data, dtype=int, delimiter=asbytes(','))
+        data = TextIO('1,2,3,4\n')
+        test = np.ndfromtxt(data, dtype=int, delimiter=',')
         assert_array_equal(test, control)
 
     def test_comments(self):
         "Test the stripping of comments"
         control = np.array([1, 2, 3, 5], int)
         # Comment on its own line
-        data = StringIO('# comment\n1,2,3,5\n')
-        test = np.ndfromtxt(data, dtype=int, delimiter=asbytes(','), comments=asbytes('#'))
+        data = TextIO('# comment\n1,2,3,5\n')
+        test = np.ndfromtxt(data, dtype=int, delimiter=',', comments='#')
         assert_equal(test, control)
         # Comment at the end of a line
-        data = StringIO('1,2,3,5# comment\n')
-        test = np.ndfromtxt(data, dtype=int, delimiter=asbytes(','), comments=asbytes('#'))
+        data = TextIO('1,2,3,5# comment\n')
+        test = np.ndfromtxt(data, dtype=int, delimiter=',', comments='#')
         assert_equal(test, control)
 
     def test_skiprows(self):
         "Test row skipping"
         control = np.array([1, 2, 3, 5], int)
-        kwargs = dict(dtype=int, delimiter=asbytes(','))
+        kwargs = dict(dtype=int, delimiter=',')
         #
-        data = StringIO('comment\n1,2,3,5\n')
+        data = TextIO('comment\n1,2,3,5\n')
         test = np.ndfromtxt(data, skip_header=1, **kwargs)
         assert_equal(test, control)
         #
-        data = StringIO('# comment\n1,2,3,5\n')
+        data = TextIO('# comment\n1,2,3,5\n')
         test = np.loadtxt(data, skiprows=1, **kwargs)
         assert_equal(test, control)
 
@@ -794,7 +808,7 @@ class TestFromTxt(TestCase):
         data.extend(["%i,%3.1f,%03s" % (i, i, i) for i in range(51)])
         data[-1] = "99,99"
         kwargs = dict(delimiter=",", names=True, skip_header=5, skip_footer=10)
-        test = np.genfromtxt(StringIO(asbytes("\n".join(data))), **kwargs)
+        test = np.genfromtxt(TextIO("\n".join(data)), **kwargs)
         ctrl = np.array([("%f" % i, "%f" % i, "%f" % i) for i in range(41)],
                         dtype=[(_, float) for _ in "ABC"])
         assert_equal(test, ctrl)
@@ -807,19 +821,19 @@ class TestFromTxt(TestCase):
             warnings.filterwarnings("ignore")
             # Footer too small to get rid of all invalid values
             assert_raises(ValueError, np.genfromtxt,
-                          StringIO(basestr), skip_footer=1)
+                          TextIO(basestr), skip_footer=1)
     #        except ValueError:
     #            pass
-            a = np.genfromtxt(StringIO(basestr), skip_footer=1, invalid_raise=False)
+            a = np.genfromtxt(TextIO(basestr), skip_footer=1, invalid_raise=False)
             assert_equal(a, np.array([[1., 1.], [2., 2.], [3., 3.], [4., 4.]]))
             #
-            a = np.genfromtxt(StringIO(basestr), skip_footer=3)
+            a = np.genfromtxt(TextIO(basestr), skip_footer=3)
             assert_equal(a, np.array([[1., 1.], [2., 2.], [3., 3.], [4., 4.]]))
             #
             basestr = '1 1\n2  \n3 3\n4 4\n5  \n6 6\n7 7\n'
-            a = np.genfromtxt(StringIO(basestr), skip_footer=1, invalid_raise=False)
+            a = np.genfromtxt(TextIO(basestr), skip_footer=1, invalid_raise=False)
             assert_equal(a, np.array([[1., 1.], [3., 3.], [4., 4.], [6., 6.]]))
-            a = np.genfromtxt(StringIO(basestr), skip_footer=3, invalid_raise=False)
+            a = np.genfromtxt(TextIO(basestr), skip_footer=3, invalid_raise=False)
             assert_equal(a, np.array([[1., 1.], [3., 3.], [4., 4.]]))
         finally:
             warn_ctx.__exit__()
@@ -827,9 +841,9 @@ class TestFromTxt(TestCase):
 
     def test_header(self):
         "Test retrieving a header"
-        data = StringIO('gender age weight\nM 64.0 75.0\nF 25.0 60.0')
+        data = TextIO('gender age weight\nM 64.0 75.0\nF 25.0 60.0')
         test = np.ndfromtxt(data, dtype=None, names=True)
-        control = {'gender': np.array(asbytes_nested(['M', 'F'])),
+        control = {'gender': np.array([b'M', b'F']),
                    'age': np.array([64.0, 25.0]),
                    'weight': np.array([75.0, 60.0])}
         assert_equal(test['gender'], control['gender'])
@@ -838,9 +852,9 @@ class TestFromTxt(TestCase):
 
     def test_auto_dtype(self):
         "Test the automatic definition of the output dtype"
-        data = StringIO('A 64 75.0 3+4j True\nBCD 25 60.0 5+6j False')
+        data = TextIO('A 64 75.0 3+4j True\nBCD 25 60.0 5+6j False')
         test = np.ndfromtxt(data, dtype=None)
-        control = [np.array(asbytes_nested(['A', 'BCD'])),
+        control = [np.array([b'A', b'BCD']),
                    np.array([64, 25]),
                    np.array([75.0, 60.0]),
                    np.array([3 + 4j, 5 + 6j]),
@@ -852,7 +866,7 @@ class TestFromTxt(TestCase):
 
     def test_auto_dtype_uniform(self):
         "Tests whether the output dtype can be uniformized"
-        data = StringIO('1 2 3 4\n5 6 7 8\n')
+        data = TextIO('1 2 3 4\n5 6 7 8\n')
         test = np.ndfromtxt(data, dtype=None)
         control = np.array([[1, 2, 3, 4], [5, 6, 7, 8]])
         assert_equal(test, control)
@@ -860,7 +874,7 @@ class TestFromTxt(TestCase):
 
     def test_fancy_dtype(self):
         "Check that a nested dtype isn't MIA"
-        data = StringIO('1,2,3.0\n4,5,6.0\n')
+        data = TextIO('1,2,3.0\n4,5,6.0\n')
         fancydtype = np.dtype([('x', int), ('y', [('t', int), ('s', float)])])
         test = np.ndfromtxt(data, dtype=fancydtype, delimiter=',')
         control = np.array([(1, (2, 3.0)), (4, (5, 6.0))], dtype=fancydtype)
@@ -871,7 +885,7 @@ class TestFromTxt(TestCase):
         "Test overwriting the names of the dtype"
         descriptor = {'names': ('g', 'a', 'w'),
                       'formats': ('S1', 'i4', 'f4')}
-        data = StringIO('M 64.0 75.0\nF 25.0 60.0')
+        data = TextIO(b'M 64.0 75.0\nF 25.0 60.0')
         names = ('gender', 'age', 'weight')
         test = np.ndfromtxt(data, dtype=descriptor, names=names)
         descriptor['names'] = names
@@ -882,7 +896,7 @@ class TestFromTxt(TestCase):
 
     def test_commented_header(self):
         "Check that names can be retrieved even if the line is commented out."
-        data = StringIO("""
+        data = TextIO("""
 #gender age weight
 M   21  72.100000
 F   35  58.330000
@@ -894,7 +908,7 @@ M   33  21.99
                   dtype=[('gender', '|S1'), ('age', int), ('weight', float)])
         assert_equal(test, ctrl)
         # Ditto, but we should get rid of the first element
-        data = StringIO("""
+        data = TextIO(b"""
 # gender age weight
 M   21  72.100000
 F   35  58.330000
@@ -906,7 +920,7 @@ M   33  21.99
 
     def test_autonames_and_usecols(self):
         "Tests names and usecols"
-        data = StringIO('A B C D\n aaaa 121 45 9.1')
+        data = TextIO('A B C D\n aaaa 121 45 9.1')
         test = np.ndfromtxt(data, usecols=('A', 'C', 'D'),
                             names=True, dtype=None)
         control = np.array(('aaaa', 45, 9.1),
@@ -916,7 +930,7 @@ M   33  21.99
 
     def test_converters_with_usecols(self):
         "Test the combination user-defined converters and usecol"
-        data = StringIO('1,2,3,,5\n6,7,8,9,10\n')
+        data = TextIO('1,2,3,,5\n6,7,8,9,10\n')
         test = np.ndfromtxt(data, dtype=int, delimiter=',',
                             converters={3:lambda s: int(s or - 999)},
                             usecols=(1, 3,))
@@ -925,7 +939,7 @@ M   33  21.99
 
     def test_converters_with_usecols_and_names(self):
         "Tests names and usecols"
-        data = StringIO('A B C D\n aaaa 121 45 9.1')
+        data = TextIO('A B C D\n aaaa 121 45 9.1')
         test = np.ndfromtxt(data, usecols=('A', 'C', 'D'), names=True,
                             dtype=None, converters={'C':lambda s: 2 * int(s)})
         control = np.array(('aaaa', 90, 9.1),
@@ -935,26 +949,26 @@ M   33  21.99
     def test_converters_cornercases(self):
         "Test the conversion to datetime."
         converter = {'date': lambda s: strptime(s, '%Y-%m-%d %H:%M:%SZ')}
-        data = StringIO('2009-02-03 12:00:00Z, 72214.0')
+        data = TextIO('2009-02-03 12:00:00Z, 72214.0')
         test = np.ndfromtxt(data, delimiter=',', dtype=None,
                             names=['date', 'stid'], converters=converter)
-        control = np.array((datetime(2009, 02, 03), 72214.),
+        control = np.array((datetime(2009, 2, 3), 72214.),
                            dtype=[('date', np.object_), ('stid', float)])
         assert_equal(test, control)
 
     def test_converters_cornercases2(self):
         "Test the conversion to datetime64."
         converter = {'date': lambda s: np.datetime64(strptime(s, '%Y-%m-%d %H:%M:%SZ'))}
-        data = StringIO('2009-02-03 12:00:00Z, 72214.0')
+        data = TextIO('2009-02-03 12:00:00Z, 72214.0')
         test = np.ndfromtxt(data, delimiter=',', dtype=None,
                             names=['date', 'stid'], converters=converter)
-        control = np.array((datetime(2009, 02, 03), 72214.),
+        control = np.array((datetime(2009, 2, 3), 72214.),
                            dtype=[('date', 'datetime64[us]'), ('stid', float)])
         assert_equal(test, control)
 
     def test_unused_converter(self):
         "Test whether unused converters are forgotten"
-        data = StringIO("1 21\n  3 42\n")
+        data = TextIO("1 21\n  3 42\n")
         test = np.ndfromtxt(data, usecols=(1,),
                             converters={0: lambda s: int(s, 16)})
         assert_equal(test, [21, 42])
@@ -966,11 +980,11 @@ M   33  21.99
 
 
     def test_invalid_converter(self):
-        strip_rand = lambda x : float((asbytes('r') in x.lower() and x.split()[-1]) or
-                                      (not asbytes('r') in x.lower() and x.strip() or 0.0))
-        strip_per = lambda x : float((asbytes('%') in x.lower() and x.split()[0]) or
-                                     (not asbytes('%') in x.lower() and x.strip() or 0.0))
-        s = StringIO("D01N01,10/1/2003 ,1 %,R 75,400,600\r\n" \
+        strip_rand = lambda x : float((b'r' in x.lower() and x.split()[-1]) or
+                                      (b'r' not in x.lower() and x.strip() or 0.0))
+        strip_per = lambda x : float((b'%' in x.lower() and x.split()[0]) or
+                                     (b'%' not in x.lower() and x.strip() or 0.0))
+        s = TextIO("D01N01,10/1/2003 ,1 %,R 75,400,600\r\n"
                               "L24U05,12/5/2003, 2 %,1,300, 150.5\r\n"
                               "D02N03,10/10/2004,R 1,,7,145.55")
         kwargs = dict(converters={2 : strip_per, 3 : strip_rand}, delimiter=",",
@@ -979,7 +993,7 @@ M   33  21.99
 
     def test_tricky_converter_bug1666(self):
         "Test some corner case"
-        s = StringIO('q1,2\nq3,4')
+        s = TextIO('q1,2\nq3,4')
         cnv = lambda s:float(s[1:])
         test = np.genfromtxt(s, delimiter=',', converters={0:cnv})
         control = np.array([[1., 2.], [3., 4.]])
@@ -989,12 +1003,12 @@ M   33  21.99
 
     def test_dtype_with_converters(self):
         dstr = "2009; 23; 46"
-        test = np.ndfromtxt(StringIO(dstr,),
+        test = np.ndfromtxt(TextIO(dstr,),
                             delimiter=";", dtype=float, converters={0:bytes})
         control = np.array([('2009', 23., 46)],
                            dtype=[('f0', '|S4'), ('f1', float), ('f2', float)])
         assert_equal(test, control)
-        test = np.ndfromtxt(StringIO(dstr,),
+        test = np.ndfromtxt(TextIO(dstr,),
                             delimiter=";", dtype=float, converters={0:float})
         control = np.array([2009., 23., 46],)
         assert_equal(test, control)
@@ -1004,12 +1018,12 @@ M   33  21.99
         "Test using an explicit dtype with an object"
         from datetime import date
         import time
-        data = asbytes(""" 1; 2001-01-01
-                           2; 2002-01-31 """)
+        data = """ 1; 2001-01-01
+                   2; 2002-01-31 """
         ndtype = [('idx', int), ('code', np.object)]
         func = lambda s: strptime(s.strip(), "%Y-%m-%d")
         converters = {1: func}
-        test = np.genfromtxt(StringIO(data), delimiter=";", dtype=ndtype,
+        test = np.genfromtxt(TextIO(data), delimiter=";", dtype=ndtype,
                              converters=converters)
         control = np.array([(1, datetime(2001, 1, 1)), (2, datetime(2002, 1, 31))],
                            dtype=ndtype)
@@ -1017,7 +1031,7 @@ M   33  21.99
         #
         ndtype = [('nest', [('idx', int), ('code', np.object)])]
         try:
-            test = np.genfromtxt(StringIO(data), delimiter=";",
+            test = np.genfromtxt(TextIO(data), delimiter=";",
                                  dtype=ndtype, converters=converters)
         except NotImplementedError:
             pass
@@ -1028,7 +1042,7 @@ M   33  21.99
 
     def test_userconverters_with_explicit_dtype(self):
         "Test user_converters w/ explicit (standard) dtype"
-        data = StringIO('skip,skip,2001-01-01,1.0,skip')
+        data = TextIO('skip,skip,2001-01-01,1.0,skip')
         test = np.genfromtxt(data, delimiter=",", names=None, dtype=float,
                              usecols=(2, 3), converters={2: bytes})
         control = np.array([('2001-01-01', 1.)],
@@ -1038,7 +1052,7 @@ M   33  21.99
 
     def test_spacedelimiter(self):
         "Test space delimiter"
-        data = StringIO("1  2  3  4   5\n6  7  8  9  10")
+        data = TextIO("1  2  3  4   5\n6  7  8  9  10")
         test = np.ndfromtxt(data)
         control = np.array([[ 1., 2., 3., 4., 5.],
                             [ 6., 7., 8., 9., 10.]])
@@ -1047,13 +1061,13 @@ M   33  21.99
     def test_integer_delimiter(self):
         "Test using an integer for delimiter"
         data = "  1  2  3\n  4  5 67\n890123  4"
-        test = np.genfromtxt(StringIO(data), delimiter=3)
+        test = np.genfromtxt(TextIO(data), delimiter=3)
         control = np.array([[1, 2, 3], [4, 5, 67], [890, 123, 4]])
         assert_equal(test, control)
 
 
     def test_missing(self):
-        data = StringIO('1,2,3,,5\n')
+        data = TextIO('1,2,3,,5\n')
         test = np.ndfromtxt(data, dtype=int, delimiter=',', \
                             converters={3:lambda s: int(s or - 999)})
         control = np.array([1, 2, 3, -999, 5], int)
@@ -1063,7 +1077,7 @@ M   33  21.99
     def test_missing_with_tabs(self):
         "Test w/ a delimiter tab"
         txt = "1\t2\t3\n\t2\t\n1\t\t3"
-        test = np.genfromtxt(StringIO(txt), delimiter="\t",
+        test = np.genfromtxt(TextIO(txt), delimiter="\t",
                              usemask=True,)
         ctrl_d = np.array([(1, 2, 3), (np.nan, 2, np.nan), (1, np.nan, 3)],)
         ctrl_m = np.array([(0, 0, 0), (1, 0, 1), (0, 1, 0)], dtype=bool)
@@ -1075,14 +1089,14 @@ M   33  21.99
         "Test the selection of columns"
         # Select 1 column
         control = np.array([[1, 2], [3, 4]], float)
-        data = StringIO()
+        data = TextIO()
         np.savetxt(data, control)
         data.seek(0)
         test = np.ndfromtxt(data, dtype=float, usecols=(1,))
         assert_equal(test, control[:, 1])
         #
         control = np.array([[1, 2, 3], [3, 4, 5]], float)
-        data = StringIO()
+        data = TextIO()
         np.savetxt(data, control)
         data.seek(0)
         test = np.ndfromtxt(data, dtype=float, usecols=(1, 2))
@@ -1095,23 +1109,23 @@ M   33  21.99
     def test_usecols_as_css(self):
         "Test giving usecols with a comma-separated string"
         data = "1 2 3\n4 5 6"
-        test = np.genfromtxt(StringIO(data),
+        test = np.genfromtxt(TextIO(data),
                              names="a, b, c", usecols="a, c")
         ctrl = np.array([(1, 3), (4, 6)], dtype=[(_, float) for _ in "ac"])
         assert_equal(test, ctrl)
 
     def test_usecols_with_structured_dtype(self):
         "Test usecols with an explicit structured dtype"
-        data = StringIO("""JOE 70.1 25.3\nBOB 60.5 27.9""")
+        data = TextIO("JOE 70.1 25.3\nBOB 60.5 27.9")
         names = ['stid', 'temp']
         dtypes = ['S4', 'f8']
         test = np.ndfromtxt(data, usecols=(0, 2), dtype=zip(names, dtypes))
-        assert_equal(test['stid'], asbytes_nested(["JOE", "BOB"]))
+        assert_equal(test['stid'], [b"JOE", b"BOB"])
         assert_equal(test['temp'], [25.3, 27.9])
 
     def test_usecols_with_integer(self):
         "Test usecols with an integer"
-        test = np.genfromtxt(StringIO("1 2 3\n4 5 6"), usecols=0)
+        test = np.genfromtxt(TextIO(b"1 2 3\n4 5 6"), usecols=0)
         assert_equal(test, np.array([1., 4.]))
 
     def test_usecols_with_named_columns(self):
@@ -1119,9 +1133,9 @@ M   33  21.99
         ctrl = np.array([(1, 3), (4, 6)], dtype=[('a', float), ('c', float)])
         data = "1 2 3\n4 5 6"
         kwargs = dict(names="a, b, c")
-        test = np.genfromtxt(StringIO(data), usecols=(0, -1), **kwargs)
+        test = np.genfromtxt(TextIO(data), usecols=(0, -1), **kwargs)
         assert_equal(test, ctrl)
-        test = np.genfromtxt(StringIO(data),
+        test = np.genfromtxt(TextIO(data),
                              usecols=('a', 'c'), **kwargs)
         assert_equal(test, ctrl)
 
@@ -1131,7 +1145,7 @@ M   33  21.99
         warn_ctx.__enter__()
         try:
             warnings.filterwarnings("ignore", message="genfromtxt: Empty input file:")
-            data = StringIO()
+            data = TextIO()
             test = np.genfromtxt(data)
             assert_equal(test, np.array([]))
         finally:
@@ -1139,7 +1153,7 @@ M   33  21.99
 
     def test_fancy_dtype_alt(self):
         "Check that a nested dtype isn't MIA"
-        data = StringIO('1,2,3.0\n4,5,6.0\n')
+        data = TextIO('1,2,3.0\n4,5,6.0\n')
         fancydtype = np.dtype([('x', int), ('y', [('t', int), ('s', float)])])
         test = np.mafromtxt(data, dtype=fancydtype, delimiter=',')
         control = ma.array([(1, (2, 3.0)), (4, (5, 6.0))], dtype=fancydtype)
@@ -1147,7 +1161,7 @@ M   33  21.99
 
 
     def test_shaped_dtype(self):
-        c = StringIO("aaaa  1.0  8.0  1 2 3 4 5 6")
+        c = TextIO("aaaa  1.0  8.0  1 2 3 4 5 6")
         dt = np.dtype([('name', 'S4'), ('x', float), ('y', float),
                        ('block', int, (2, 3))])
         x = np.ndfromtxt(c, dtype=dt)
@@ -1156,7 +1170,7 @@ M   33  21.99
         assert_array_equal(x, a)
 
     def test_withmissing(self):
-        data = StringIO('A,B\n0,1\n2,N/A')
+        data = TextIO('A,B\n0,1\n2,N/A')
         kwargs = dict(delimiter=",", missing_values="N/A", names=True)
         test = np.mafromtxt(data, dtype=None, **kwargs)
         control = ma.array([(0, 1), (2, -1)],
@@ -1179,7 +1193,7 @@ M   33  21.99
         basekwargs = dict(dtype=None, delimiter=",", names=True,)
         mdtype = [('A', int), ('B', float), ('C', complex)]
         #
-        test = np.mafromtxt(StringIO(data), missing_values="N/A",
+        test = np.mafromtxt(TextIO(data), missing_values="N/A",
                             **basekwargs)
         control = ma.array([(0, 0.0, 0j), (1, -999, 1j),
                             (-9, 2.2, -999j), (3, -99, 3j)],
@@ -1188,7 +1202,7 @@ M   33  21.99
         assert_equal(test, control)
         #
         basekwargs['dtype'] = mdtype
-        test = np.mafromtxt(StringIO(data),
+        test = np.mafromtxt(TextIO(data),
                             missing_values={0:-9, 1:-99, 2:-999j}, **basekwargs)
         control = ma.array([(0, 0.0, 0j), (1, -999, 1j),
                             (-9, 2.2, -999j), (3, -99, 3j)],
@@ -1196,7 +1210,7 @@ M   33  21.99
                             dtype=mdtype)
         assert_equal(test, control)
         #
-        test = np.mafromtxt(StringIO(data),
+        test = np.mafromtxt(TextIO(data),
                             missing_values={0:-9, 'B':-99, 'C':-999j},
                             **basekwargs)
         control = ma.array([(0, 0.0, 0j), (1, -999, 1j),
@@ -1214,18 +1228,18 @@ M   33  21.99
                       names="a,b,c",
                       missing_values={0:"N/A", 'b':" ", 2:"???"},
                       filling_values={0:0, 'b':0, 2:-999})
-        test = np.genfromtxt(StringIO(data), **kwargs)
+        test = np.genfromtxt(TextIO(data), **kwargs)
         ctrl = np.array([(0, 2, 3), (4, 0, -999)],
                         dtype=[(_, int) for _ in "abc"])
         assert_equal(test, ctrl)
         #
-        test = np.genfromtxt(StringIO(data), usecols=(0, -1), **kwargs)
+        test = np.genfromtxt(TextIO(data), usecols=(0, -1), **kwargs)
         ctrl = np.array([(0, 3), (4, -999)], dtype=[(_, int) for _ in "ac"])
         assert_equal(test, ctrl)
 
 
     def test_withmissing_float(self):
-        data = StringIO('A,B\n0,1.5\n2,-999.00')
+        data = TextIO('A,B\n0,1.5\n2,-999.00')
         test = np.mafromtxt(data, dtype=None, delimiter=',',
                             missing_values='-999.0', names=True,)
         control = ma.array([(0, 1.5), (2, -1.)],
@@ -1237,7 +1251,7 @@ M   33  21.99
 
     def test_with_masked_column_uniform(self):
         "Test masked column"
-        data = StringIO('1 2 3\n4 5 6\n')
+        data = TextIO('1 2 3\n4 5 6\n')
         test = np.genfromtxt(data, dtype=None,
                              missing_values='2,5', usemask=True)
         control = ma.array([[1, 2, 3], [4, 5, 6]], mask=[[0, 1, 0], [0, 1, 0]])
@@ -1245,7 +1259,7 @@ M   33  21.99
 
     def test_with_masked_column_various(self):
         "Test masked column"
-        data = StringIO('True 2 3\nFalse 5 6\n')
+        data = TextIO('True 2 3\nFalse 5 6\n')
         test = np.genfromtxt(data, dtype=None,
                              missing_values='2,5', usemask=True)
         control = ma.array([(1, 2, 3), (0, 5, 6)],
@@ -1260,7 +1274,7 @@ M   33  21.99
         for i in range(5):
             data[10 * i] = "2, 2, 2, 2 2"
         data.insert(0, "a, b, c, d, e")
-        mdata = StringIO("\n".join(data))
+        mdata = TextIO("\n".join(data))
         #
         kwargs = dict(delimiter=",", dtype=None, names=True)
         # XXX: is there a better way to get the return value of the callable in
@@ -1283,7 +1297,7 @@ M   33  21.99
         for i in range(5):
             data[10 * i] = "2, 2, 2, 2 2"
         data.insert(0, "a, b, c, d, e")
-        mdata = StringIO("\n".join(data))
+        mdata = TextIO("\n".join(data))
         kwargs = dict(delimiter=",", dtype=None, names=True,
                       invalid_raise=False)
         # XXX: is there a better way to get the return value of the callable in
@@ -1307,7 +1321,7 @@ M   33  21.99
     def test_inconsistent_dtype(self):
         "Test inconsistent dtype"
         data = ["1, 1, 1, 1, -1.1"] * 50
-        mdata = StringIO("\n".join(data))
+        mdata = TextIO("\n".join(data))
 
         converters = {4: lambda x:"(%s)" % x}
         kwargs = dict(delimiter=",", converters=converters,
@@ -1318,7 +1332,7 @@ M   33  21.99
     def test_default_field_format(self):
         "Test default format"
         data = "0, 1, 2.3\n4, 5, 6.7"
-        mtest = np.ndfromtxt(StringIO(data),
+        mtest = np.ndfromtxt(TextIO(data),
                              delimiter=",", dtype=None, defaultfmt="f%02i")
         ctrl = np.array([(0, 1, 2.3), (4, 5, 6.7)],
                         dtype=[("f00", int), ("f01", int), ("f02", float)])
@@ -1327,7 +1341,7 @@ M   33  21.99
     def test_single_dtype_wo_names(self):
         "Test single dtype w/o names"
         data = "0, 1, 2.3\n4, 5, 6.7"
-        mtest = np.ndfromtxt(StringIO(data),
+        mtest = np.ndfromtxt(TextIO(data),
                              delimiter=",", dtype=float, defaultfmt="f%02i")
         ctrl = np.array([[0., 1., 2.3], [4., 5., 6.7]], dtype=float)
         assert_equal(mtest, ctrl)
@@ -1335,7 +1349,7 @@ M   33  21.99
     def test_single_dtype_w_explicit_names(self):
         "Test single dtype w explicit names"
         data = "0, 1, 2.3\n4, 5, 6.7"
-        mtest = np.ndfromtxt(StringIO(data),
+        mtest = np.ndfromtxt(TextIO(data),
                              delimiter=",", dtype=float, names="a, b, c")
         ctrl = np.array([(0., 1., 2.3), (4., 5., 6.7)],
                         dtype=[(_, float) for _ in "abc"])
@@ -1344,7 +1358,7 @@ M   33  21.99
     def test_single_dtype_w_implicit_names(self):
         "Test single dtype w implicit names"
         data = "a, b, c\n0, 1, 2.3\n4, 5, 6.7"
-        mtest = np.ndfromtxt(StringIO(data),
+        mtest = np.ndfromtxt(TextIO(data),
                              delimiter=",", dtype=float, names=True)
         ctrl = np.array([(0., 1., 2.3), (4., 5., 6.7)],
                         dtype=[(_, float) for _ in "abc"])
@@ -1353,7 +1367,7 @@ M   33  21.99
     def test_easy_structured_dtype(self):
         "Test easy structured dtype"
         data = "0, 1, 2.3\n4, 5, 6.7"
-        mtest = np.ndfromtxt(StringIO(data), delimiter=",",
+        mtest = np.ndfromtxt(TextIO(data), delimiter=",",
                              dtype=(int, float, float), defaultfmt="f_%02i")
         ctrl = np.array([(0, 1., 2.3), (4, 5., 6.7)],
                         dtype=[("f_00", int), ("f_01", float), ("f_02", float)])
@@ -1363,11 +1377,11 @@ M   33  21.99
         "Test autostrip"
         data = "01/01/2003  , 1.3,   abcde"
         kwargs = dict(delimiter=",", dtype=None)
-        mtest = np.ndfromtxt(StringIO(data), **kwargs)
+        mtest = np.ndfromtxt(TextIO(data), **kwargs)
         ctrl = np.array([('01/01/2003  ', 1.3, '   abcde')],
                         dtype=[('f0', '|S12'), ('f1', float), ('f2', '|S8')])
         assert_equal(mtest, ctrl)
-        mtest = np.ndfromtxt(StringIO(data), autostrip=True, **kwargs)
+        mtest = np.ndfromtxt(TextIO(data), autostrip=True, **kwargs)
         ctrl = np.array([('01/01/2003', 1.3, 'abcde')],
                         dtype=[('f0', '|S10'), ('f1', float), ('f2', '|S5')])
         assert_equal(mtest, ctrl)
@@ -1376,20 +1390,20 @@ M   33  21.99
         "Test the 'replace_space' option"
         txt = "A.A, B (B), C:C\n1, 2, 3.14"
         # Test default: replace ' ' by '_' and delete non-alphanum chars
-        test = np.genfromtxt(StringIO(txt),
+        test = np.genfromtxt(TextIO(txt),
                              delimiter=",", names=True, dtype=None)
         ctrl_dtype = [("AA", int), ("B_B", int), ("CC", float)]
         ctrl = np.array((1, 2, 3.14), dtype=ctrl_dtype)
         assert_equal(test, ctrl)
         # Test: no replace, no delete
-        test = np.genfromtxt(StringIO(txt),
+        test = np.genfromtxt(TextIO(txt),
                              delimiter=",", names=True, dtype=None,
                              replace_space='', deletechars='')
         ctrl_dtype = [("A.A", int), ("B (B)", int), ("C:C", float)]
         ctrl = np.array((1, 2, 3.14), dtype=ctrl_dtype)
         assert_equal(test, ctrl)
         # Test: no delete (spaces are replaced by _)
-        test = np.genfromtxt(StringIO(txt),
+        test = np.genfromtxt(TextIO(txt),
                              delimiter=",", names=True, dtype=None,
                              deletechars='')
         ctrl_dtype = [("A.A", int), ("B_(B)", int), ("C:C", float)]
@@ -1403,17 +1417,17 @@ M   33  21.99
         # w/ dtype=None
         ctrl = np.array([(0, 1, 2), (3, 4, 5)],
                         dtype=[(_, int) for _ in ('A', 'f0', 'C')])
-        test = np.ndfromtxt(StringIO(data), dtype=None, **kwargs)
+        test = np.ndfromtxt(TextIO(data), dtype=None, **kwargs)
         assert_equal(test, ctrl)
         # w/ default dtype
         ctrl = np.array([(0, 1, 2), (3, 4, 5)],
                         dtype=[(_, float) for _ in ('A', 'f0', 'C')])
-        test = np.ndfromtxt(StringIO(data), **kwargs)
+        test = np.ndfromtxt(TextIO(data), **kwargs)
 
     def test_names_auto_completion(self):
         "Make sure that names are properly completed"
         data = "1 2 3\n 4 5 6"
-        test = np.genfromtxt(StringIO(data),
+        test = np.genfromtxt(TextIO(data),
                              dtype=(int, float, int), names="a")
         ctrl = np.array([(1, 2, 3), (4, 5, 6)],
                         dtype=[('a', int), ('f0', float), ('f1', int)])
@@ -1423,17 +1437,17 @@ M   33  21.99
         "Make sure we pick up the right names w/ usecols"
         data = "A,B,C,D,E\n0,1,2,3,4\n0,1,2,3,4\n0,1,2,3,4"
         ctrl_names = ("A", "C", "E")
-        test = np.genfromtxt(StringIO(data),
+        test = np.genfromtxt(TextIO(data),
                              dtype=(int, int, int), delimiter=",",
                              usecols=(0, 2, 4), names=True)
         assert_equal(test.dtype.names, ctrl_names)
         #
-        test = np.genfromtxt(StringIO(data),
+        test = np.genfromtxt(TextIO(data),
                              dtype=(int, int, int), delimiter=",",
                              usecols=("A", "C", "E"), names=True)
         assert_equal(test.dtype.names, ctrl_names)
         #
-        test = np.genfromtxt(StringIO(data),
+        test = np.genfromtxt(TextIO(data),
                              dtype=int, delimiter=",",
                              usecols=("A", "C", "E"), names=True)
         assert_equal(test.dtype.names, ctrl_names)
@@ -1444,35 +1458,35 @@ M   33  21.99
         kwargs = dict(delimiter=(5, 5, 4), names=True, dtype=None)
         ctrl = np.array([(0, 1, 2.3), (45, 67, 9.)],
                         dtype=[('A', int), ('B', int), ('C', float)])
-        test = np.ndfromtxt(StringIO(data), **kwargs)
+        test = np.ndfromtxt(TextIO(data), **kwargs)
         assert_equal(test, ctrl)
         #
         kwargs = dict(delimiter=5, names=True, dtype=None)
         ctrl = np.array([(0, 1, 2.3), (45, 67, 9.)],
                         dtype=[('A', int), ('B', int), ('C', float)])
-        test = np.ndfromtxt(StringIO(data), **kwargs)
+        test = np.ndfromtxt(TextIO(data), **kwargs)
         assert_equal(test, ctrl)
 
     def test_filling_values(self):
         "Test missing values"
-        data = "1, 2, 3\n1, , 5\n0, 6, \n"
+        data = b"1, 2, 3\n1, , 5\n0, 6, \n"
         kwargs = dict(delimiter=",", dtype=None, filling_values= -999)
         ctrl = np.array([[1, 2, 3], [1, -999, 5], [0, 6, -999]], dtype=int)
-        test = np.ndfromtxt(StringIO(data), **kwargs)
+        test = np.ndfromtxt(TextIO(data), **kwargs)
         assert_equal(test, ctrl)
 
     def test_comments_is_none(self):
         # Github issue 329 (None was previously being converted to 'None').
-        test = np.genfromtxt(StringIO("test1,testNonetherestofthedata"),
+        test = np.genfromtxt(TextIO("test1,testNonetherestofthedata"),
                              dtype=None, comments=None, delimiter=',')
-        assert_equal(test[1], asbytes('testNonetherestofthedata'))
-        test = np.genfromtxt(StringIO("test1, testNonetherestofthedata"),
+        assert_equal(test[1], b'testNonetherestofthedata')
+        test = np.genfromtxt(TextIO("test1, testNonetherestofthedata"),
                              dtype=None, comments=None, delimiter=',')
-        assert_equal(test[1], asbytes(' testNonetherestofthedata'))
+        assert_equal(test[1], b' testNonetherestofthedata')
 
     def test_recfromtxt(self):
         #
-        data = StringIO('A,B\n0,1\n2,3')
+        data = TextIO('A,B\n0,1\n2,3')
         kwargs = dict(delimiter=",", missing_values="N/A", names=True)
         test = np.recfromtxt(data, **kwargs)
         control = np.array([(0, 1), (2, 3)],
@@ -1480,7 +1494,7 @@ M   33  21.99
         self.assertTrue(isinstance(test, np.recarray))
         assert_equal(test, control)
         #
-        data = StringIO('A,B\n0,1\n2,N/A')
+        data = TextIO('A,B\n0,1\n2,N/A')
         test = np.recfromtxt(data, dtype=None, usemask=True, **kwargs)
         control = ma.array([(0, 1), (2, -1)],
                            mask=[(False, False), (False, True)],
@@ -1491,7 +1505,7 @@ M   33  21.99
 
     def test_recfromcsv(self):
         #
-        data = StringIO('A,B\n0,1\n2,3')
+        data = TextIO('A,B\n0,1\n2,3')
         kwargs = dict(missing_values="N/A", names=True, case_sensitive=True)
         test = np.recfromcsv(data, dtype=None, **kwargs)
         control = np.array([(0, 1), (2, 3)],
@@ -1499,7 +1513,7 @@ M   33  21.99
         self.assertTrue(isinstance(test, np.recarray))
         assert_equal(test, control)
         #
-        data = StringIO('A,B\n0,1\n2,N/A')
+        data = TextIO('A,B\n0,1\n2,N/A')
         test = np.recfromcsv(data, dtype=None, usemask=True, **kwargs)
         control = ma.array([(0, 1), (2, -1)],
                            mask=[(False, False), (False, True)],
@@ -1508,7 +1522,7 @@ M   33  21.99
         assert_equal(test.mask, control.mask)
         assert_equal(test.A, [0, 2])
         #
-        data = StringIO('A,B\n0,1\n2,3')
+        data = TextIO('A,B\n0,1\n2,3')
         test = np.recfromcsv(data, missing_values='N/A',)
         control = np.array([(0, 1), (2, 3)],
                            dtype=[('a', np.int), ('b', np.int)])
@@ -1537,6 +1551,7 @@ M   33  21.99
                 os.unlink(name)
 
     def test_gft_using_generator(self):
+        # gft doesn't work with unicode.
         def count():
             for i in range(10):
                 yield asbytes("%d" % i)
@@ -1548,7 +1563,7 @@ M   33  21.99
 def test_gzip_load():
     a = np.random.random((5, 5))
 
-    s = StringIO()
+    s = BytesIO()
     f = gzip.GzipFile(fileobj=s, mode="w")
 
     np.save(f, a)
@@ -1565,9 +1580,9 @@ def test_gzip_loadtxt():
     # reopened by another open call. So we first put the gzipped string
     # of the test reference array, write it to a securely opened file,
     # which is then read from by the loadtxt function
-    s = StringIO()
+    s = BytesIO()
     g = gzip.GzipFile(fileobj=s, mode='w')
-    g.write(asbytes('1 2 3\n'))
+    g.write(b'1 2 3\n')
     g.close()
     s.seek(0)
 
@@ -1581,9 +1596,9 @@ def test_gzip_loadtxt():
         os.unlink(name)
 
 def test_gzip_loadtxt_from_string():
-    s = StringIO()
+    s = BytesIO()
     f = gzip.GzipFile(fileobj=s, mode="w")
-    f.write(asbytes('1 2 3\n'))
+    f.write(b'1 2 3\n')
     f.close()
     s.seek(0)
 
@@ -1591,7 +1606,7 @@ def test_gzip_loadtxt_from_string():
     assert_array_equal(np.loadtxt(f), [1, 2, 3])
 
 def test_npzfile_dict():
-    s = StringIO()
+    s = BytesIO()
     x = np.zeros((3, 3))
     y = np.zeros((3, 3))
 
@@ -1620,7 +1635,7 @@ def test_load_refcount():
     # Check that objects returned by np.load are directly freed based on
     # their refcount, rather than needing the gc to collect them.
 
-    f = StringIO()
+    f = BytesIO()
     np.savez(f, [1, 2, 3])
     f.seek(0)
 
diff --git a/numpy/lib/tests/test_regression.py b/numpy/lib/tests/test_regression.py
index 9e303d2b1..2e76b320c 100644
--- a/numpy/lib/tests/test_regression.py
+++ b/numpy/lib/tests/test_regression.py
@@ -1,5 +1,6 @@
 from __future__ import division, absolute_import
 
+import sys
 from numpy.testing import *
 from numpy.testing.utils import _assert_valid_refcount
 import numpy as np
@@ -202,7 +203,11 @@ class TestRegression(TestCase):
 
     def test_loadtxt_fields_subarrays(self):
         # For ticket #1936
-        from StringIO import StringIO
+        if sys.version_info[0] >= 3:
+            from io import StringIO
+        else:
+            from StringIO import StringIO
+
         dt = [("a", 'u1', 2), ("b", 'u1', 2)]
         x = np.loadtxt(StringIO("0 1 2 3"), dtype=dt)
         assert_equal(x, np.array([((0, 1), (2, 3))], dtype=dt))
diff --git a/numpy/lib/tests/test_utils.py b/numpy/lib/tests/test_utils.py
index 4b386e0b1..8cec1887b 100644
--- a/numpy/lib/tests/test_utils.py
+++ b/numpy/lib/tests/test_utils.py
@@ -1,10 +1,14 @@
 from __future__ import division, absolute_import
 
+import sys
 from numpy.testing import *
 import numpy.lib.utils as utils
 from numpy.lib import deprecate
 
-from StringIO import StringIO
+if sys.version_info[0] >= 3:
+    from io import StringIO
+else:
+    from StringIO import StringIO
 
 def test_lookfor():
     out = StringIO()
diff --git a/numpy/lib/utils.py b/numpy/lib/utils.py
index 9a8776098..b81db681e 100644
--- a/numpy/lib/utils.py
+++ b/numpy/lib/utils.py
@@ -848,7 +848,12 @@ def _lookfor_generate_cache(module, import_modules, regenerate):
     global _lookfor_caches
     # Local import to speed up numpy's import time.
     import inspect
-    from cStringIO import StringIO
+
+    if sys.version_info[0] >= 3:
+        # In Python3 stderr, stdout are text files.
+        from io import StringIO
+    else:
+        from StringIO import StringIO
 
     if module is None:
         module = "numpy"
-- 
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