Merged revisions 70364 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r70364 | eric.smith | 2009-03-14 07:57:26 -0400 (Sat, 14 Mar 2009) | 17 lines

  Issue 5237, Allow auto-numbered replacement fields in str.format() strings.

  For simple uses for str.format(), this makes the typing easier. Hopfully this
  will help in the adoption of str.format().

  For example:
  'The {} is {}'.format('sky', 'blue')

  You can mix and matcth auto-numbering and named replacement fields:
  'The {} is {color}'.format('sky', color='blue')

  But you can't mix and match auto-numbering and specified numbering:
  'The {0} is {}'.format('sky', 'blue')
  ValueError: cannot switch from manual field specification to automatic field numbering

  Will port to 3.1.
........

Lib/test/test_unicode.py

@@ -683,9 +683,9 @@ class UnicodeTest(
         self.assertRaises(ValueError, "{0!}".format, 0)
         self.assertRaises(ValueError, "{0!rs}".format, 0)
         self.assertRaises(ValueError, "{!}".format)
-        self.assertRaises(ValueError, "{:}".format)
-        self.assertRaises(ValueError, "{:s}".format)
-        self.assertRaises(ValueError, "{}".format)
+        self.assertRaises(IndexError, "{:}".format)
+        self.assertRaises(IndexError, "{:s}".format)
+        self.assertRaises(IndexError, "{}".format)
 
         # can't have a replacement on the field name portion
         self.assertRaises(TypeError, '{0[{1}]}'.format, 'abcdefg', 4)
@@ -704,6 +704,36 @@ class UnicodeTest(
         self.assertRaises(ValueError, format, '', '#')
         self.assertRaises(ValueError, format, '', '#20')
 
+    def test_format_auto_numbering(self):
+        class C:
+            def __init__(self, x=100):
+                self._x = x
+            def __format__(self, spec):
+                return spec
+
+        self.assertEqual('{}'.format(10), '10')
+        self.assertEqual('{:5}'.format('s'), 's    ')
+        self.assertEqual('{!r}'.format('s'), "'s'")
+        self.assertEqual('{._x}'.format(C(10)), '10')
+        self.assertEqual('{[1]}'.format([1, 2]), '2')
+        self.assertEqual('{[a]}'.format({'a':4, 'b':2}), '4')
+        self.assertEqual('a{}b{}c'.format(0, 1), 'a0b1c')
+
+        self.assertEqual('a{:{}}b'.format('x', '^10'), 'a    x     b')
+        self.assertEqual('a{:{}x}b'.format(20, '#'), 'a0x14b')
+
+        # can't mix and match numbering and auto-numbering
+        self.assertRaises(ValueError, '{}{1}'.format, 1, 2)
+        self.assertRaises(ValueError, '{1}{}'.format, 1, 2)
+        self.assertRaises(ValueError, '{:{1}}'.format, 1, 2)
+        self.assertRaises(ValueError, '{0:{}}'.format, 1, 2)
+
+        # can mix and match auto-numbering and named
+        self.assertEqual('{f}{}'.format(4, f='test'), 'test4')
+        self.assertEqual('{}{f}'.format(4, f='test'), '4test')
+        self.assertEqual('{:{f}}{g}{}'.format(1, 3, g='g', f=2), ' 1g3')
+        self.assertEqual('{f:{}}{}{g}'.format(2, 4, f=1, g='g'), ' 14g')
+
     def test_formatting(self):
         string_tests.MixinStrUnicodeUserStringTest.test_formatting(self)
         # Testing Unicode formatting strings...

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 3.1 alpha 2?
 Core and Builtins
 -----------------
 
+- Issue #5237: Allow auto-numbered fields in str.format(). For
+  example: '{} {}'.format(1, 2) == '1 2'.
+
 - Issue #5392: when a very low recursion limit was set, the interpreter would
   abort with a fatal error after the recursion limit was hit twice.
 
@@ -33,6 +36,7 @@ What's New in Python 3.1 alpha 1
 Core and Builtins
 -----------------
 
+=======
 - The io module has been reimplemented in C for speed.
 
 - Give dict views an informative __repr__.