Issue #7094: Add alternate ('#') flag to __format__ methods for float, complex and Decimal. Allows greater control over when decimal points appear. Added to make transitioning from %-formatting easier. '#g' still has a problem with Decimal which I'll fix soon.

5 files changed, 61 insertions, 17 deletions

diff --git a/Lib/decimal.py b/Lib/decimal.py
index 5a9f840771..f379ee57ce 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -5991,7 +5991,7 @@ _exact_half = re.compile('50*$').match
 #
 # A format specifier for Decimal looks like:
 #
-#   [[fill]align][sign][0][minimumwidth][,][.precision][type]
+#   [[fill]align][sign][#][0][minimumwidth][,][.precision][type]
 
 _parse_format_specifier_regex = re.compile(r"""\A
 (?:
@@ -5999,6 +5999,7 @@ _parse_format_specifier_regex = re.compile(r"""\A
    (?P<align>[<>=^])
 )?
 (?P<sign>[-+ ])?
+(?P<alt>\#)?
 (?P<zeropad>0)?
 (?P<minimumwidth>(?!0)\d+)?
 (?P<thousands_sep>,)?
@@ -6214,7 +6215,7 @@ def _format_number(is_negative, intpart, fracpart, exp, spec):
 
     sign = _format_sign(is_negative, spec)
 
-    if fracpart:
+    if fracpart or spec['alt']:
         fracpart = spec['decimal_point'] + fracpart
 
     if exp != 0 or spec['type'] in 'eE':
diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
index 2810b36718..cc21aa7a62 100644
--- a/Lib/test/test_complex.py
+++ b/Lib/test/test_complex.py
@@ -555,8 +555,28 @@ class ComplexTest(unittest.TestCase):
         self.assertEqual(format(1.5e21+3j, '^40,.2f'), ' 1,500,000,000,000,000,000,000.00+3.00j ')
         self.assertEqual(format(1.5e21+3000j, ',.2f'), '1,500,000,000,000,000,000,000.00+3,000.00j')
 
-        # alternate is invalid
-        self.assertRaises(ValueError, (1.5+0.5j).__format__, '#f')
+        # Issue 7094: Alternate formatting (specified by #)
+        self.assertEqual(format(1+1j, '.0e'), '1e+00+1e+00j')
+        self.assertEqual(format(1+1j, '#.0e'), '1.e+00+1.e+00j')
+        self.assertEqual(format(1+1j, '.0f'), '1+1j')
+        self.assertEqual(format(1+1j, '#.0f'), '1.+1.j')
+        self.assertEqual(format(1.1+1.1j, 'g'), '1.1+1.1j')
+        self.assertEqual(format(1.1+1.1j, '#g'), '1.10000+1.10000j')
+
+        # Alternate doesn't make a difference for these, they format the same with or without it
+        self.assertEqual(format(1+1j, '.1e'),  '1.0e+00+1.0e+00j')
+        self.assertEqual(format(1+1j, '#.1e'), '1.0e+00+1.0e+00j')
+        self.assertEqual(format(1+1j, '.1f'),  '1.0+1.0j')
+        self.assertEqual(format(1+1j, '#.1f'), '1.0+1.0j')
+
+        # Misc. other alternate tests
+        self.assertEqual(format((-1.5+0.5j), '#f'), '-1.500000+0.500000j')
+        self.assertEqual(format((-1.5+0.5j), '#.0f'), '-2.+0.j')
+        self.assertEqual(format((-1.5+0.5j), '#e'), '-1.500000e+00+5.000000e-01j')
+        self.assertEqual(format((-1.5+0.5j), '#.0e'), '-2.e+00+5.e-01j')
+        self.assertEqual(format((-1.5+0.5j), '#g'), '-1.50000+0.500000j')
+        self.assertEqual(format((-1.5+0.5j), '.0g'), '-2+0.5j')
+        self.assertEqual(format((-1.5+0.5j), '#.0g'), '-2.+0.5j')
 
         # zero padding is invalid
         self.assertRaises(ValueError, (1.5+0.5j).__format__, '010f')
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 611ef55007..3036170aeb 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -818,6 +818,18 @@ class DecimalFormatTest(unittest.TestCase):
 
             # issue 6850
             ('a=-7.0', '0.12345', 'aaaa0.1'),
+
+            # Issue 7094: Alternate formatting (specified by #)
+            ('.0e', '1.0', '1e+0'),
+            ('#.0e', '1.0', '1.e+0'),
+            ('.0f', '1.0', '1'),
+            ('#.0f', '1.0', '1.'),
+            ('g', '1.1', '1.1'),
+            ('#g', '1.1', '1.1'),
+            ('.0g', '1', '1'),
+            ('#.0g', '1', '1.'),
+            ('.0%', '1.0', '100%'),
+            ('#.0%', '1.0', '100.%'),
             ]
         for fmt, d, result in test_values:
             self.assertEqual(format(Decimal(d), fmt), result)
diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
index e0479db274..0072133aae 100644
--- a/Lib/test/test_float.py
+++ b/Lib/test/test_float.py
@@ -706,11 +706,8 @@ class RoundTestCase(unittest.TestCase):
         def test(fmt, value, expected):
             # Test with both % and format().
             self.assertEqual(fmt % value, expected, fmt)
-            if not '#' in fmt:
-                # Until issue 7094 is implemented, format() for floats doesn't
-                #  support '#' formatting
-                fmt = fmt[1:] # strip off the %
-                self.assertEqual(format(value, fmt), expected, fmt)
+            fmt = fmt[1:] # strip off the %
+            self.assertEqual(format(value, fmt), expected, fmt)
 
         for fmt in ['%e', '%f', '%g', '%.0e', '%.6f', '%.20g',
                     '%#e', '%#f', '%#g', '%#.20e', '%#.15f', '%#.3g']:
diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index d16dbba173..8a98a03567 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -396,13 +396,9 @@ class TypesTests(unittest.TestCase):
             self.assertEqual(len(format(0, cfmt)), len(format(x, cfmt)))
 
     def test_float__format__(self):
-        # these should be rewritten to use both format(x, spec) and
-        # x.__format__(spec)
-
         def test(f, format_spec, result):
-            assert type(f) == float
-            assert type(format_spec) == str
             self.assertEqual(f.__format__(format_spec), result)
+            self.assertEqual(format(f, format_spec), result)
 
         test(0.0, 'f', '0.000000')
 
@@ -516,9 +512,27 @@ class TypesTests(unittest.TestCase):
                 self.assertRaises(ValueError, format, 1e-100, format_spec)
                 self.assertRaises(ValueError, format, -1e-100, format_spec)
 
-        # Alternate formatting is not supported
-        self.assertRaises(ValueError, format, 0.0, '#')
-        self.assertRaises(ValueError, format, 0.0, '#20f')
+        # Alternate float formatting
+        test(1.0, '.0e', '1e+00')
+        test(1.0, '#.0e', '1.e+00')
+        test(1.0, '.0f', '1')
+        test(1.0, '#.0f', '1.')
+        test(1.1, 'g', '1.1')
+        test(1.1, '#g', '1.10000')
+        test(1.0, '.0%', '100%')
+        test(1.0, '#.0%', '100.%')
+
+        # Issue 7094: Alternate formatting (specified by #)
+        test(1.0, '0e',  '1.000000e+00')
+        test(1.0, '#0e', '1.000000e+00')
+        test(1.0, '0f',  '1.000000' )
+        test(1.0, '#0f', '1.000000')
+        test(1.0, '.1e',  '1.0e+00')
+        test(1.0, '#.1e', '1.0e+00')
+        test(1.0, '.1f',  '1.0')
+        test(1.0, '#.1f', '1.0')
+        test(1.0, '.1%',  '100.0%')
+        test(1.0, '#.1%', '100.0%')
 
         # Issue 6902
         test(12345.6, "0<20", '12345.60000000000000')