Merge pull request #5489 from charris/cleanup-gh-5156

Cleanup gh 5156

2 files changed, 14 insertions, 2 deletions

diff --git a/numpy/lib/npyio.py b/numpy/lib/npyio.py
index bedd0e941..a40de4fea 100644
--- a/numpy/lib/npyio.py
+++ b/numpy/lib/npyio.py
@@ -729,7 +729,8 @@ def loadtxt(fname, dtype=float, comments='#', delimiter=None,
 
     """
     # Type conversions for Py3 convenience
-    comments = asbytes(comments)
+    if comments is not None:
+        comments = asbytes(comments)
     user_converters = converters
     if delimiter is not None:
         delimiter = asbytes(delimiter)
@@ -802,7 +803,10 @@ def loadtxt(fname, dtype=float, comments='#', delimiter=None,
 
     def split_line(line):
         """Chop off comments, strip, and split at delimiter."""
-        line = asbytes(line).split(comments)[0].strip(asbytes('\r\n'))
+        if comments is None:
+            line = asbytes(line).strip(asbytes('\r\n'))
+        else:
+            line = asbytes(line).split(comments)[0].strip(asbytes('\r\n'))
         if line:
             return line.split(delimiter)
         else:
diff --git a/numpy/lib/tests/test_io.py b/numpy/lib/tests/test_io.py
index 68b2018cd..81bddfadd 100644
--- a/numpy/lib/tests/test_io.py
+++ b/numpy/lib/tests/test_io.py
@@ -786,6 +786,14 @@ class TestLoadTxt(TestCase):
         # Check for exception and that exception contains line number
         assert_raises_regex(ValueError, "3", np.loadtxt, c)
 
+    def test_none_as_string(self):
+        # gh-5155, None should work as string when format demands it
+        c = TextIO()
+        c.write('100,foo,200\n300,None,400')
+        c.seek(0)
+        dt = np.dtype([('x', int), ('a', 'S10'), ('y', int)])
+        data = np.loadtxt(c, delimiter=',', dtype=dt, comments=None)
+
 
 class Testfromregex(TestCase):
     # np.fromregex expects files opened in binary mode.