Backport of PEP 3101, Advanced String Formatting, from py3k.

Highlights:
 - Adding PyObject_Format.
 - Adding string.Format class.
 - Adding __format__ for str, unicode, int, long, float, datetime.
 - Adding builtin format.
 - Adding ''.format and u''.format.
 - str/unicode fixups for formatters.

The files in Objects/stringlib that implement PEP 3101 (stringdefs.h,
unicodedefs.h, formatter.h, string_format.h) are identical in trunk
and py3k.  Any changes from here on should be made to trunk, and
changes will propogate to py3k).

8 files changed, 1141 insertions, 0 deletions

diff --git a/Lib/string.py b/Lib/string.py
index 9e3cc41..eb680c2 100644
--- a/Lib/string.py
+++ b/Lib/string.py
@@ -527,3 +527,115 @@ try:
     letters = lowercase + uppercase
 except ImportError:
     pass                                          # Use the original versions
+
+########################################################################
+# the Formatter class
+# see PEP 3101 for details and purpose of this class
+
+# The hard parts are reused from the C implementation.  They're
+# exposed here via the sys module.  sys was chosen because it's always
+# available and doesn't have to be dynamically loaded.
+
+# The overall parser is implemented in str._formatter_parser.
+# The field name parser is implemented in str._formatter_field_name_split
+
+class Formatter(object):
+    def format(self, format_string, *args, **kwargs):
+        return self.vformat(format_string, args, kwargs)
+
+    def vformat(self, format_string, args, kwargs):
+        used_args = set()
+        result = self._vformat(format_string, args, kwargs, used_args, 2)
+        self.check_unused_args(used_args, args, kwargs)
+        return result
+
+    def _vformat(self, format_string, args, kwargs, used_args, recursion_depth):
+        if recursion_depth < 0:
+            raise ValueError('Max string recursion exceeded')
+        result = []
+        for literal_text, field_name, format_spec, conversion in \
+                self.parse(format_string):
+
+            # output the literal text
+            if literal_text:
+                result.append(literal_text)
+
+            # if there's a field, output it
+            if field_name is not None:
+                # this is some markup, find the object and do
+                #  the formatting
+
+                # given the field_name, find the object it references
+                #  and the argument it came from
+                obj, arg_used = self.get_field(field_name, args, kwargs)
+                used_args.add(arg_used)
+
+                # do any conversion on the resulting object
+                obj = self.convert_field(obj, conversion)
+
+                # expand the format spec, if needed
+                format_spec = self._vformat(format_spec, args, kwargs,
+                                            used_args, recursion_depth-1)
+
+                # format the object and append to the result
+                result.append(self.format_field(obj, format_spec))
+
+        return ''.join(result)
+
+
+    def get_value(self, key, args, kwargs):
+        if isinstance(key, (int, long)):
+            return args[key]
+        else:
+            return kwargs[key]
+
+
+    def check_unused_args(self, used_args, args, kwargs):
+        pass
+
+
+    def format_field(self, value, format_spec):
+        return format(value, format_spec)
+
+
+    def convert_field(self, value, conversion):
+        # do any conversion on the resulting object
+        if conversion == 'r':
+            return repr(value)
+        elif conversion == 's':
+            return str(value)
+        elif conversion is None:
+            return value
+        raise ValueError("Unknown converion specifier {0!s}".format(conversion))
+
+
+    # returns an iterable that contains tuples of the form:
+    # (literal_text, field_name, format_spec, conversion)
+    # literal_text can be zero length
+    # field_name can be None, in which case there's no
+    #  object to format and output
+    # if field_name is not None, it is looked up, formatted
+    #  with format_spec and conversion and then used
+    def parse(self, format_string):
+        return format_string._formatter_parser()
+
+
+    # given a field_name, find the object it references.
+    #  field_name:   the field being looked up, e.g. "0.name"
+    #                 or "lookup[3]"
+    #  used_args:    a set of which args have been used
+    #  args, kwargs: as passed in to vformat
+    def get_field(self, field_name, args, kwargs):
+        first, rest = field_name._formatter_field_name_split()
+
+        obj = self.get_value(first, args, kwargs)
+
+        # loop through the rest of the field_name, doing
+        #  getattr or getitem as needed
+        for is_attr, i in rest:
+            if is_attr:
+                obj = getattr(obj, i)
+            else:
+                obj = obj[i]
+
+        return obj, first
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index ddc5842..a5d1f92 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -2012,6 +2012,101 @@ class TestSorted(unittest.TestCase):
         data = 'The quick Brown fox Jumped over The lazy Dog'.split()
         self.assertRaises(TypeError, sorted, data, None, lambda x,y: 0)
 
+    def test_format(self):
+        # Test the basic machinery of the format() builtin.  Don't test
+        #  the specifics of the various formatters
+        self.assertEqual(format(3, ''), '3')
+
+        # Returns some classes to use for various tests.  There's
+        #  an old-style version, and a new-style version
+        def classes_new():
+            class A(object):
+                def __init__(self, x):
+                    self.x = x
+                def __format__(self, format_spec):
+                    return str(self.x) + format_spec
+            class DerivedFromA(A):
+                pass
+
+            class Simple(object): pass
+            class DerivedFromSimple(Simple):
+                def __init__(self, x):
+                    self.x = x
+                def __format__(self, format_spec):
+                    return str(self.x) + format_spec
+            class DerivedFromSimple2(DerivedFromSimple): pass
+            return A, DerivedFromA, DerivedFromSimple, DerivedFromSimple2
+
+        # In 3.0, classes_classic has the same meaning as classes_new
+        def classes_classic():
+            class A:
+                def __init__(self, x):
+                    self.x = x
+                def __format__(self, format_spec):
+                    return str(self.x) + format_spec
+            class DerivedFromA(A):
+                pass
+
+            class Simple: pass
+            class DerivedFromSimple(Simple):
+                def __init__(self, x):
+                    self.x = x
+                def __format__(self, format_spec):
+                    return str(self.x) + format_spec
+            class DerivedFromSimple2(DerivedFromSimple): pass
+            return A, DerivedFromA, DerivedFromSimple, DerivedFromSimple2
+
+        def class_test(A, DerivedFromA, DerivedFromSimple, DerivedFromSimple2):
+            self.assertEqual(format(A(3), 'spec'), '3spec')
+            self.assertEqual(format(DerivedFromA(4), 'spec'), '4spec')
+            self.assertEqual(format(DerivedFromSimple(5), 'abc'), '5abc')
+            self.assertEqual(format(DerivedFromSimple2(10), 'abcdef'),
+                             '10abcdef')
+
+        class_test(*classes_new())
+        class_test(*classes_classic())
+
+        def empty_format_spec(value):
+            # test that:
+            #  format(x, '') == str(x)
+            #  format(x) == str(x)
+            self.assertEqual(format(value, ""), str(value))
+            self.assertEqual(format(value), str(value))
+
+        # for builtin types, format(x, "") == str(x)
+        empty_format_spec(17**13)
+        empty_format_spec(1.0)
+        empty_format_spec(3.1415e104)
+        empty_format_spec(-3.1415e104)
+        empty_format_spec(3.1415e-104)
+        empty_format_spec(-3.1415e-104)
+        empty_format_spec(object)
+        empty_format_spec(None)
+
+        # TypeError because self.__format__ returns the wrong type
+        class BadFormatResult:
+            def __format__(self, format_spec):
+                return 1.0
+        self.assertRaises(TypeError, format, BadFormatResult(), "")
+
+        # TypeError because format_spec is not unicode or str
+        self.assertRaises(TypeError, format, object(), 4)
+        self.assertRaises(TypeError, format, object(), object())
+
+        # tests for object.__format__ really belong elsewhere, but
+        #  there's no good place to put them
+        x = object().__format__('')
+        self.assert_(x.startswith('<object object at'))
+
+        # first argument to object.__format__ must be string
+        self.assertRaises(TypeError, object().__format__, 3)
+        self.assertRaises(TypeError, object().__format__, object())
+        self.assertRaises(TypeError, object().__format__, None)
+
+        # make sure we can take a subclass of str as a format spec
+        class DerivedFromStr(str): pass
+        self.assertEqual(format(0, DerivedFromStr('10')), '         0')
+
 def test_main(verbose=None):
     test_classes = (BuiltinTest, TestSorted)
 
diff --git a/Lib/test/test_datetime.py b/Lib/test/test_datetime.py
index 21b8890..cb639b4 100644
--- a/Lib/test/test_datetime.py
+++ b/Lib/test/test_datetime.py
@@ -854,6 +854,32 @@ class TestDate(HarmlessMixedComparison, unittest.TestCase):
         # A naive object replaces %z and %Z w/ empty strings.
         self.assertEqual(t.strftime("'%z' '%Z'"), "'' ''")
 
+    def test_format(self):
+        dt = self.theclass(2007, 9, 10)
+        self.assertEqual(dt.__format__(''), str(dt))
+
+        # check that a derived class's __str__() gets called
+        class A(self.theclass):
+            def __str__(self):
+                return 'A'
+        a = A(2007, 9, 10)
+        self.assertEqual(a.__format__(''), 'A')
+
+        # check that a derived class's strftime gets called
+        class B(self.theclass):
+            def strftime(self, format_spec):
+                return 'B'
+        b = B(2007, 9, 10)
+        self.assertEqual(b.__format__(''), str(dt))
+
+        for fmt in ["m:%m d:%d y:%y",
+                    "m:%m d:%d y:%y H:%H M:%M S:%S",
+                    "%z %Z",
+                    ]:
+            self.assertEqual(dt.__format__(fmt), dt.strftime(fmt))
+            self.assertEqual(a.__format__(fmt), dt.strftime(fmt))
+            self.assertEqual(b.__format__(fmt), 'B')
+
     def test_resolution_info(self):
         self.assert_(isinstance(self.theclass.min, self.theclass))
         self.assert_(isinstance(self.theclass.max, self.theclass))
@@ -1136,6 +1162,32 @@ class TestDateTime(TestDate):
         # str is ISO format with the separator forced to a blank.
         self.assertEqual(str(t), "0002-03-02 00:00:00")
 
+    def test_format(self):
+        dt = self.theclass(2007, 9, 10, 4, 5, 1, 123)
+        self.assertEqual(dt.__format__(''), str(dt))
+
+        # check that a derived class's __str__() gets called
+        class A(self.theclass):
+            def __str__(self):
+                return 'A'
+        a = A(2007, 9, 10, 4, 5, 1, 123)
+        self.assertEqual(a.__format__(''), 'A')
+
+        # check that a derived class's strftime gets called
+        class B(self.theclass):
+            def strftime(self, format_spec):
+                return 'B'
+        b = B(2007, 9, 10, 4, 5, 1, 123)
+        self.assertEqual(b.__format__(''), str(dt))
+
+        for fmt in ["m:%m d:%d y:%y",
+                    "m:%m d:%d y:%y H:%H M:%M S:%S",
+                    "%z %Z",
+                    ]:
+            self.assertEqual(dt.__format__(fmt), dt.strftime(fmt))
+            self.assertEqual(a.__format__(fmt), dt.strftime(fmt))
+            self.assertEqual(b.__format__(fmt), 'B')
+
     def test_more_ctime(self):
         # Test fields that TestDate doesn't touch.
         import time
@@ -1767,6 +1819,30 @@ class TestTime(HarmlessMixedComparison, unittest.TestCase):
         # A naive object replaces %z and %Z with empty strings.
         self.assertEqual(t.strftime("'%z' '%Z'"), "'' ''")
 
+    def test_format(self):
+        t = self.theclass(1, 2, 3, 4)
+        self.assertEqual(t.__format__(''), str(t))
+
+        # check that a derived class's __str__() gets called
+        class A(self.theclass):
+            def __str__(self):
+                return 'A'
+        a = A(1, 2, 3, 4)
+        self.assertEqual(a.__format__(''), 'A')
+
+        # check that a derived class's strftime gets called
+        class B(self.theclass):
+            def strftime(self, format_spec):
+                return 'B'
+        b = B(1, 2, 3, 4)
+        self.assertEqual(b.__format__(''), str(t))
+
+        for fmt in ['%H %M %S',
+                    ]:
+            self.assertEqual(t.__format__(fmt), t.strftime(fmt))
+            self.assertEqual(a.__format__(fmt), t.strftime(fmt))
+            self.assertEqual(b.__format__(fmt), 'B')
+
     def test_str(self):
         self.assertEqual(str(self.theclass(1, 2, 3, 4)), "01:02:03.000004")
         self.assertEqual(str(self.theclass(10, 2, 3, 4000)), "10:02:03.004000")
diff --git a/Lib/test/test_descrtut.py b/Lib/test/test_descrtut.py
index 9dcfca1..94e9845 100644
--- a/Lib/test/test_descrtut.py
+++ b/Lib/test/test_descrtut.py
@@ -183,6 +183,7 @@ Instead, you can get the same information from the list type:
      '__delslice__',
      '__doc__',
      '__eq__',
+     '__format__',
      '__ge__',
      '__getattribute__',
      '__getitem__',
diff --git a/Lib/test/test_str.py b/Lib/test/test_str.py
index 3acb6d1..7ea46bb 100644
--- a/Lib/test/test_str.py
+++ b/Lib/test/test_str.py
@@ -93,6 +93,264 @@ class StrTest(
             return
         self.assertRaises(OverflowError, 't\tt\t'.expandtabs, sys.maxint)
 
+    def test__format__(self):
+        def test(value, format, expected):
+            # test both with and without the trailing 's'
+            self.assertEqual(value.__format__(format), expected)
+            self.assertEqual(value.__format__(format + 's'), expected)
+
+        test('', '', '')
+        test('abc', '', 'abc')
+        test('abc', '.3', 'abc')
+        test('ab', '.3', 'ab')
+        test('abcdef', '.3', 'abc')
+        test('abcdef', '.0', '')
+        test('abc', '3.3', 'abc')
+        test('abc', '2.3', 'abc')
+        test('abc', '2.2', 'ab')
+        test('abc', '3.2', 'ab ')
+        test('result', 'x<0', 'result')
+        test('result', 'x<5', 'result')
+        test('result', 'x<6', 'result')
+        test('result', 'x<7', 'resultx')
+        test('result', 'x<8', 'resultxx')
+        test('result', ' <7', 'result ')
+        test('result', '<7', 'result ')
+        test('result', '>7', ' result')
+        test('result', '>8', '  result')
+        test('result', '^8', ' result ')
+        test('result', '^9', ' result  ')
+        test('result', '^10', '  result  ')
+        test('a', '10000', 'a' + ' ' * 9999)
+        test('', '10000', ' ' * 10000)
+        test('', '10000000', ' ' * 10000000)
+
+    def test_format(self):
+        self.assertEqual(''.format(), '')
+        self.assertEqual('a'.format(), 'a')
+        self.assertEqual('ab'.format(), 'ab')
+        self.assertEqual('a{{'.format(), 'a{')
+        self.assertEqual('a}}'.format(), 'a}')
+        self.assertEqual('{{b'.format(), '{b')
+        self.assertEqual('}}b'.format(), '}b')
+        self.assertEqual('a{{b'.format(), 'a{b')
+
+        # examples from the PEP:
+        import datetime
+        self.assertEqual("My name is {0}".format('Fred'), "My name is Fred")
+        self.assertEqual("My name is {0[name]}".format(dict(name='Fred')),
+                         "My name is Fred")
+        self.assertEqual("My name is {0} :-{{}}".format('Fred'),
+                         "My name is Fred :-{}")
+
+        d = datetime.date(2007, 8, 18)
+        self.assertEqual("The year is {0.year}".format(d),
+                         "The year is 2007")
+
+        # classes we'll use for testing
+        class C:
+            def __init__(self, x=100):
+                self._x = x
+            def __format__(self, spec):
+                return spec
+
+        class D:
+            def __init__(self, x):
+                self.x = x
+            def __format__(self, spec):
+                return str(self.x)
+
+        # class with __str__, but no __format__
+        class E:
+            def __init__(self, x):
+                self.x = x
+            def __str__(self):
+                return 'E(' + self.x + ')'
+
+        # class with __repr__, but no __format__ or __str__
+        class F:
+            def __init__(self, x):
+                self.x = x
+            def __repr__(self):
+                return 'F(' + self.x + ')'
+
+        # class with __format__ that forwards to string, for some format_spec's
+        class G:
+            def __init__(self, x):
+                self.x = x
+            def __str__(self):
+                return "string is " + self.x
+            def __format__(self, format_spec):
+                if format_spec == 'd':
+                    return 'G(' + self.x + ')'
+                return object.__format__(self, format_spec)
+
+        # class that returns a bad type from __format__
+        class H:
+            def __format__(self, format_spec):
+                return 1.0
+
+        class I(datetime.date):
+            def __format__(self, format_spec):
+                return self.strftime(format_spec)
+
+        class J(int):
+            def __format__(self, format_spec):
+                return int.__format__(self * 2, format_spec)
+
+
+        self.assertEqual(''.format(), '')
+        self.assertEqual('abc'.format(), 'abc')
+        self.assertEqual('{0}'.format('abc'), 'abc')
+        self.assertEqual('{0:}'.format('abc'), 'abc')
+        self.assertEqual('X{0}'.format('abc'), 'Xabc')
+        self.assertEqual('{0}X'.format('abc'), 'abcX')
+        self.assertEqual('X{0}Y'.format('abc'), 'XabcY')
+        self.assertEqual('{1}'.format(1, 'abc'), 'abc')
+        self.assertEqual('X{1}'.format(1, 'abc'), 'Xabc')
+        self.assertEqual('{1}X'.format(1, 'abc'), 'abcX')
+        self.assertEqual('X{1}Y'.format(1, 'abc'), 'XabcY')
+        self.assertEqual('{0}'.format(-15), '-15')
+        self.assertEqual('{0}{1}'.format(-15, 'abc'), '-15abc')
+        self.assertEqual('{0}X{1}'.format(-15, 'abc'), '-15Xabc')
+        self.assertEqual('{{'.format(), '{')
+        self.assertEqual('}}'.format(), '}')
+        self.assertEqual('{{}}'.format(), '{}')
+        self.assertEqual('{{x}}'.format(), '{x}')
+        self.assertEqual('{{{0}}}'.format(123), '{123}')
+        self.assertEqual('{{{{0}}}}'.format(), '{{0}}')
+        self.assertEqual('}}{{'.format(), '}{')
+        self.assertEqual('}}x{{'.format(), '}x{')
+
+        # weird field names
+        self.assertEqual("{0[foo-bar]}".format({'foo-bar':'baz'}), 'baz')
+        self.assertEqual("{0[foo bar]}".format({'foo bar':'baz'}), 'baz')
+        self.assertEqual("{0[ ]}".format({' ':3}), '3')
+
+        self.assertEqual('{foo._x}'.format(foo=C(20)), '20')
+        self.assertEqual('{1}{0}'.format(D(10), D(20)), '2010')
+        self.assertEqual('{0._x.x}'.format(C(D('abc'))), 'abc')
+        self.assertEqual('{0[0]}'.format(['abc', 'def']), 'abc')
+        self.assertEqual('{0[1]}'.format(['abc', 'def']), 'def')
+        self.assertEqual('{0[1][0]}'.format(['abc', ['def']]), 'def')
+        self.assertEqual('{0[1][0].x}'.format(['abc', [D('def')]]), 'def')
+
+        # strings
+        self.assertEqual('{0:.3s}'.format('abc'), 'abc')
+        self.assertEqual('{0:.3s}'.format('ab'), 'ab')
+        self.assertEqual('{0:.3s}'.format('abcdef'), 'abc')
+        self.assertEqual('{0:.0s}'.format('abcdef'), '')
+        self.assertEqual('{0:3.3s}'.format('abc'), 'abc')
+        self.assertEqual('{0:2.3s}'.format('abc'), 'abc')
+        self.assertEqual('{0:2.2s}'.format('abc'), 'ab')
+        self.assertEqual('{0:3.2s}'.format('abc'), 'ab ')
+        self.assertEqual('{0:x<0s}'.format('result'), 'result')
+        self.assertEqual('{0:x<5s}'.format('result'), 'result')
+        self.assertEqual('{0:x<6s}'.format('result'), 'result')
+        self.assertEqual('{0:x<7s}'.format('result'), 'resultx')
+        self.assertEqual('{0:x<8s}'.format('result'), 'resultxx')
+        self.assertEqual('{0: <7s}'.format('result'), 'result ')
+        self.assertEqual('{0:<7s}'.format('result'), 'result ')
+        self.assertEqual('{0:>7s}'.format('result'), ' result')
+        self.assertEqual('{0:>8s}'.format('result'), '  result')
+        self.assertEqual('{0:^8s}'.format('result'), ' result ')
+        self.assertEqual('{0:^9s}'.format('result'), ' result  ')
+        self.assertEqual('{0:^10s}'.format('result'), '  result  ')
+        self.assertEqual('{0:10000}'.format('a'), 'a' + ' ' * 9999)
+        self.assertEqual('{0:10000}'.format(''), ' ' * 10000)
+        self.assertEqual('{0:10000000}'.format(''), ' ' * 10000000)
+
+        # format specifiers for user defined type
+        self.assertEqual('{0:abc}'.format(C()), 'abc')
+
+        # !r and !s coersions
+        self.assertEqual('{0!s}'.format('Hello'), 'Hello')
+        self.assertEqual('{0!s:}'.format('Hello'), 'Hello')
+        self.assertEqual('{0!s:15}'.format('Hello'), 'Hello          ')
+        self.assertEqual('{0!s:15s}'.format('Hello'), 'Hello          ')
+        self.assertEqual('{0!r}'.format('Hello'), "'Hello'")
+        self.assertEqual('{0!r:}'.format('Hello'), "'Hello'")
+        self.assertEqual('{0!r}'.format(F('Hello')), 'F(Hello)')
+
+        # test fallback to object.__format__
+        self.assertEqual('{0}'.format({}), '{}')
+        self.assertEqual('{0}'.format([]), '[]')
+        self.assertEqual('{0}'.format([1]), '[1]')
+        self.assertEqual('{0}'.format(E('data')), 'E(data)')
+        self.assertEqual('{0:^10}'.format(E('data')), ' E(data)  ')
+        self.assertEqual('{0:^10s}'.format(E('data')), ' E(data)  ')
+        self.assertEqual('{0:d}'.format(G('data')), 'G(data)')
+        self.assertEqual('{0:>15s}'.format(G('data')), ' string is data')
+        self.assertEqual('{0!s}'.format(G('data')), 'string is data')
+
+        self.assertEqual("{0:date: %Y-%m-%d}".format(I(year=2007,
+                                                       month=8,
+                                                       day=27)),
+                         "date: 2007-08-27")
+
+        # test deriving from a builtin type and overriding __format__
+        self.assertEqual("{0}".format(J(10)), "20")
+
+
+        # string format specifiers
+        self.assertEqual('{0:}'.format('a'), 'a')
+
+        # computed format specifiers
+        self.assertEqual("{0:.{1}}".format('hello world', 5), 'hello')
+        self.assertEqual("{0:.{1}s}".format('hello world', 5), 'hello')
+        self.assertEqual("{0:.{precision}s}".format('hello world', precision=5), 'hello')
+        self.assertEqual("{0:{width}.{precision}s}".format('hello world', width=10, precision=5), 'hello     ')
+        self.assertEqual("{0:{width}.{precision}s}".format('hello world', width='10', precision='5'), 'hello     ')
+
+        # test various errors
+        self.assertRaises(ValueError, '{'.format)
+        self.assertRaises(ValueError, '}'.format)
+        self.assertRaises(ValueError, 'a{'.format)
+        self.assertRaises(ValueError, 'a}'.format)
+        self.assertRaises(ValueError, '{a'.format)
+        self.assertRaises(ValueError, '}a'.format)
+        self.assertRaises(IndexError, '{0}'.format)
+        self.assertRaises(IndexError, '{1}'.format, 'abc')
+        self.assertRaises(KeyError,   '{x}'.format)
+        self.assertRaises(ValueError, "}{".format)
+        self.assertRaises(ValueError, "{".format)
+        self.assertRaises(ValueError, "}".format)
+        self.assertRaises(ValueError, "abc{0:{}".format)
+        self.assertRaises(ValueError, "{0".format)
+        self.assertRaises(IndexError, "{0.}".format)
+        self.assertRaises(ValueError, "{0.}".format, 0)
+        self.assertRaises(IndexError, "{0[}".format)
+        self.assertRaises(ValueError, "{0[}".format, [])
+        self.assertRaises(KeyError,   "{0]}".format)
+        self.assertRaises(ValueError, "{0.[]}".format, 0)
+        self.assertRaises(ValueError, "{0..foo}".format, 0)
+        self.assertRaises(ValueError, "{0[0}".format, 0)
+        self.assertRaises(ValueError, "{0[0:foo}".format, 0)
+        self.assertRaises(KeyError,   "{c]}".format)
+        self.assertRaises(ValueError, "{{ {{{0}}".format, 0)
+        self.assertRaises(ValueError, "{0}}".format, 0)
+        self.assertRaises(KeyError,   "{foo}".format, bar=3)
+        self.assertRaises(ValueError, "{0!x}".format, 3)
+        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)
+
+        # can't have a replacement on the field name portion
+        self.assertRaises(TypeError, '{0[{1}]}'.format, 'abcdefg', 4)
+
+        # exceed maximum recursion depth
+        self.assertRaises(ValueError, "{0:{1:{2}}}".format, 'abc', 's', '')
+        self.assertRaises(ValueError, "{0:{1:{2:{3:{4:{5:{6}}}}}}}".format,
+                          0, 1, 2, 3, 4, 5, 6, 7)
+
+        # string format spec errors
+        self.assertRaises(ValueError, "{0:-s}".format, '')
+        self.assertRaises(ValueError, format, "", "-")
+        self.assertRaises(ValueError, "{0:=s}".format, '')
+
 
 def test_main():
     test_support.run_unittest(StrTest)
diff --git a/Lib/test/test_string.py b/Lib/test/test_string.py
index 9b22333..5c20a2b 100644
--- a/Lib/test/test_string.py
+++ b/Lib/test/test_string.py
@@ -106,6 +106,92 @@ class ModuleTest(unittest.TestCase):
         self.assertEqual(string.capwords('ABC-DEF-GHI', '-'), 'Abc-Def-Ghi')
         self.assertEqual(string.capwords('ABC-def DEF-ghi GHI'), 'Abc-def Def-ghi Ghi')
 
+    def test_formatter(self):
+        fmt = string.Formatter()
+        self.assertEqual(fmt.format("foo"), "foo")
+
+        self.assertEqual(fmt.format("foo{0}", "bar"), "foobar")
+        self.assertEqual(fmt.format("foo{1}{0}-{1}", "bar", 6), "foo6bar-6")
+        self.assertEqual(fmt.format("-{arg!r}-", arg='test'), "-'test'-")
+
+        # override get_value ############################################
+        class NamespaceFormatter(string.Formatter):
+            def __init__(self, namespace={}):
+                string.Formatter.__init__(self)
+                self.namespace = namespace
+
+            def get_value(self, key, args, kwds):
+                if isinstance(key, str):
+                    try:
+                        # Check explicitly passed arguments first
+                        return kwds[key]
+                    except KeyError:
+                        return self.namespace[key]
+                else:
+                    string.Formatter.get_value(key, args, kwds)
+
+        fmt = NamespaceFormatter({'greeting':'hello'})
+        self.assertEqual(fmt.format("{greeting}, world!"), 'hello, world!')
+
+
+        # override format_field #########################################
+        class CallFormatter(string.Formatter):
+            def format_field(self, value, format_spec):
+                return format(value(), format_spec)
+
+        fmt = CallFormatter()
+        self.assertEqual(fmt.format('*{0}*', lambda : 'result'), '*result*')
+
+
+        # override convert_field ########################################
+        class XFormatter(string.Formatter):
+            def convert_field(self, value, conversion):
+                if conversion == 'x':
+                    return None
+                return super(XFormatter, self).convert_field(value, conversion)
+
+        fmt = XFormatter()
+        self.assertEqual(fmt.format("{0!r}:{0!x}", 'foo', 'foo'), "'foo':None")
+
+
+        # override parse ################################################
+        class BarFormatter(string.Formatter):
+            # returns an iterable that contains tuples of the form:
+            # (literal_text, field_name, format_spec, conversion)
+            def parse(self, format_string):
+                for field in format_string.split('|'):
+                    if field[0] == '+':
+                        # it's markup
+                        field_name, _, format_spec = field[1:].partition(':')
+                        yield '', field_name, format_spec, None
+                    else:
+                        yield field, None, None, None
+
+        fmt = BarFormatter()
+        self.assertEqual(fmt.format('*|+0:^10s|*', 'foo'), '*   foo    *')
+
+        # test all parameters used
+        class CheckAllUsedFormatter(string.Formatter):
+            def check_unused_args(self, used_args, args, kwargs):
+                # Track which arguments actuallly got used
+                unused_args = set(kwargs.keys())
+                unused_args.update(range(0, len(args)))
+
+                for arg in used_args:
+                    unused_args.remove(arg)
+
+                if unused_args:
+                    raise ValueError("unused arguments")
+
+        fmt = CheckAllUsedFormatter()
+        self.assertEqual(fmt.format("{0}", 10), "10")
+        self.assertEqual(fmt.format("{0}{i}", 10, i=100), "10100")
+        self.assertEqual(fmt.format("{0}{i}{1}", 10, 20, i=100), "1010020")
+        self.assertRaises(ValueError, fmt.format, "{0}{i}{1}", 10, 20, i=100, j=0)
+        self.assertRaises(ValueError, fmt.format, "{0}", 10, 20)
+        self.assertRaises(ValueError, fmt.format, "{0}", 10, 20, i=100)
+        self.assertRaises(ValueError, fmt.format, "{i}", 10, 20, i=100)
+
 class BytesAliasTest(unittest.TestCase):
 
     def test_builtin(self):
diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index bded0d7..ae1bfe1 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -266,6 +266,257 @@ class TypesTests(unittest.TestCase):
         except TypeError: pass
         else: self.fail("char buffer (at C level) not working")
 
+    def test_int__format__(self):
+        def test(i, format_spec, result):
+            # just make sure I'm not accidentally checking longs
+            assert type(i) == int
+            assert type(format_spec) == str
+            self.assertEqual(i.__format__(format_spec), result)
+            self.assertEqual(i.__format__(unicode(format_spec)), result)
+
+        test(123456789, 'd', '123456789')
+        test(123456789, 'd', '123456789')
+
+        test(1, 'c', '\01')
+
+        # sign and aligning are interdependent
+        test(1, "-", '1')
+        test(-1, "-", '-1')
+        test(1, "-3", '  1')
+        test(-1, "-3", ' -1')
+        test(1, "+3", ' +1')
+        test(-1, "+3", ' -1')
+        test(1, " 3", '  1')
+        test(-1, " 3", ' -1')
+        test(1, " ", ' 1')
+        test(-1, " ", '-1')
+
+        # hex
+        test(3, "x", "3")
+        test(3, "X", "3")
+        test(1234, "x", "4d2")
+        test(-1234, "x", "-4d2")
+        test(1234, "8x", "     4d2")
+        test(-1234, "8x", "    -4d2")
+        test(1234, "x", "4d2")
+        test(-1234, "x", "-4d2")
+        test(-3, "x", "-3")
+        test(-3, "X", "-3")
+        test(int('be', 16), "x", "be")
+        test(int('be', 16), "X", "BE")
+        test(-int('be', 16), "x", "-be")
+        test(-int('be', 16), "X", "-BE")
+
+        # octal
+        test(3, "o", "3")
+        test(-3, "o", "-3")
+        test(65, "o", "101")
+        test(-65, "o", "-101")
+        test(1234, "o", "2322")
+        test(-1234, "o", "-2322")
+        test(1234, "-o", "2322")
+        test(-1234, "-o", "-2322")
+        test(1234, " o", " 2322")
+        test(-1234, " o", "-2322")
+        test(1234, "+o", "+2322")
+        test(-1234, "+o", "-2322")
+
+        # binary
+        test(3, "b", "11")
+        test(-3, "b", "-11")
+        test(1234, "b", "10011010010")
+        test(-1234, "b", "-10011010010")
+        test(1234, "-b", "10011010010")
+        test(-1234, "-b", "-10011010010")
+        test(1234, " b", " 10011010010")
+        test(-1234, " b", "-10011010010")
+        test(1234, "+b", "+10011010010")
+        test(-1234, "+b", "-10011010010")
+
+        # make sure these are errors
+
+        # precision disallowed
+        self.assertRaises(ValueError, 3 .__format__, "1.3")
+        # sign not allowed with 'c'
+        self.assertRaises(ValueError, 3 .__format__, "+c")
+        # format spec must be string
+        self.assertRaises(TypeError, 3 .__format__, None)
+        self.assertRaises(TypeError, 3 .__format__, 0)
+
+        # ensure that only int and float type specifiers work
+        for format_spec in ([chr(x) for x in range(ord('a'), ord('z')+1)] +
+                            [chr(x) for x in range(ord('A'), ord('Z')+1)]):
+            if not format_spec in 'bcdoxXeEfFgGn%':
+                self.assertRaises(ValueError, 0 .__format__, format_spec)
+                self.assertRaises(ValueError, 1 .__format__, format_spec)
+                self.assertRaises(ValueError, (-1) .__format__, format_spec)
+
+        # ensure that float type specifiers work; format converts
+        #  the int to a float
+        for format_spec in 'eEfFgGn%':
+            for value in [0, 1, -1, 100, -100, 1234567890, -1234567890]:
+                self.assertEqual(value.__format__(format_spec),
+                                 float(value).__format__(format_spec))
+
+    def test_long__format__(self):
+        def test(i, format_spec, result):
+            # make sure we're not accidentally checking ints
+            assert type(i) == long
+            assert type(format_spec) == str
+            self.assertEqual(i.__format__(format_spec), result)
+            self.assertEqual(i.__format__(unicode(format_spec)), result)
+
+        test(10**100, 'd', '1' + '0' * 100)
+        test(10**100+100, 'd', '1' + '0' * 97 + '100')
+
+        test(123456789L, 'd', '123456789')
+        test(123456789L, 'd', '123456789')
+
+        # sign and aligning are interdependent
+        test(1L, "-", '1')
+        test(-1L, "-", '-1')
+        test(1L, "-3", '  1')
+        test(-1L, "-3", ' -1')
+        test(1L, "+3", ' +1')
+        test(-1L, "+3", ' -1')
+        test(1L, " 3", '  1')
+        test(-1L, " 3", ' -1')
+        test(1L, " ", ' 1')
+        test(-1L, " ", '-1')
+
+        test(1L, 'c', '\01')
+
+        # hex
+        test(3L, "x", "3")
+        test(3L, "X", "3")
+        test(1234L, "x", "4d2")
+        test(-1234L, "x", "-4d2")
+        test(1234L, "8x", "     4d2")
+        test(-1234L, "8x", "    -4d2")
+        test(1234L, "x", "4d2")
+        test(-1234L, "x", "-4d2")
+        test(-3L, "x", "-3")
+        test(-3L, "X", "-3")
+        test(long('be', 16), "x", "be")
+        test(long('be', 16), "X", "BE")
+        test(-long('be', 16), "x", "-be")
+        test(-long('be', 16), "X", "-BE")
+
+        # octal
+        test(3L, "o", "3")
+        test(-3L, "o", "-3")
+        test(65L, "o", "101")
+        test(-65L, "o", "-101")
+        test(1234L, "o", "2322")
+        test(-1234L, "o", "-2322")
+        test(1234L, "-o", "2322")
+        test(-1234L, "-o", "-2322")
+        test(1234L, " o", " 2322")
+        test(-1234L, " o", "-2322")
+        test(1234L, "+o", "+2322")
+        test(-1234L, "+o", "-2322")
+
+        # binary
+        test(3L, "b", "11")
+        test(-3L, "b", "-11")
+        test(1234L, "b", "10011010010")
+        test(-1234L, "b", "-10011010010")
+        test(1234L, "-b", "10011010010")
+        test(-1234L, "-b", "-10011010010")
+        test(1234L, " b", " 10011010010")
+        test(-1234L, " b", "-10011010010")
+        test(1234L, "+b", "+10011010010")
+        test(-1234L, "+b", "-10011010010")
+
+        # make sure these are errors
+
+        # precision disallowed
+        self.assertRaises(ValueError, 3L .__format__, "1.3")
+        # sign not allowed with 'c'
+        self.assertRaises(ValueError, 3L .__format__, "+c")
+        # format spec must be string
+        self.assertRaises(TypeError, 3L .__format__, None)
+        self.assertRaises(TypeError, 3L .__format__, 0)
+
+        # ensure that only int and float type specifiers work
+        for format_spec in ([chr(x) for x in range(ord('a'), ord('z')+1)] +
+                            [chr(x) for x in range(ord('A'), ord('Z')+1)]):
+            if not format_spec in 'bcdoxXeEfFgGn%':
+                self.assertRaises(ValueError, 0L .__format__, format_spec)
+                self.assertRaises(ValueError, 1L .__format__, format_spec)
+                self.assertRaises(ValueError, (-1L) .__format__, format_spec)
+
+        # ensure that float type specifiers work; format converts
+        #  the long to a float
+        for format_spec in 'eEfFgGn%':
+            for value in [0L, 1L, -1L, 100L, -100L, 1234567890L, -1234567890L]:
+                self.assertEqual(value.__format__(format_spec),
+                                 float(value).__format__(format_spec))
+
+    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(f.__format__(unicode(format_spec)), result)
+
+        test(0.0, 'f', '0.000000')
+
+        # the default is 'g', except for empty format spec
+        test(0.0, '', '0.0')
+        test(0.01, '', '0.01')
+        test(0.01, 'g', '0.01')
+
+        test( 1.0, ' g', ' 1')
+        test(-1.0, ' g', '-1')
+        test( 1.0, '+g', '+1')
+        test(-1.0, '+g', '-1')
+        test(1.1234e200, 'g', '1.1234e+200')
+        test(1.1234e200, 'G', '1.1234E+200')
+
+
+        test(1.0, 'f', '1.000000')
+
+        test(-1.0, 'f', '-1.000000')
+
+        test( 1.0, ' f', ' 1.000000')
+        test(-1.0, ' f', '-1.000000')
+        test( 1.0, '+f', '+1.000000')
+        test(-1.0, '+f', '-1.000000')
+        test(1.1234e200, 'f', '1.1234e+200')
+        test(1.1234e200, 'F', '1.1234e+200')
+
+        test( 1.0, 'e', '1.000000e+00')
+        test(-1.0, 'e', '-1.000000e+00')
+        test( 1.0, 'E', '1.000000E+00')
+        test(-1.0, 'E', '-1.000000E+00')
+        test(1.1234e20, 'e', '1.123400e+20')
+        test(1.1234e20, 'E', '1.123400E+20')
+
+        # % formatting
+        test(-1.0, '%', '-100.000000%')
+
+        # format spec must be string
+        self.assertRaises(TypeError, 3.0.__format__, None)
+        self.assertRaises(TypeError, 3.0.__format__, 0)
+
+        # other format specifiers shouldn't work on floats,
+        #  in particular int specifiers
+        for format_spec in ([chr(x) for x in range(ord('a'), ord('z')+1)] +
+                            [chr(x) for x in range(ord('A'), ord('Z')+1)]):
+            if not format_spec in 'eEfFgGn%':
+                self.assertRaises(ValueError, format, 0.0, format_spec)
+                self.assertRaises(ValueError, format, 1.0, format_spec)
+                self.assertRaises(ValueError, format, -1.0, format_spec)
+                self.assertRaises(ValueError, format, 1e100, format_spec)
+                self.assertRaises(ValueError, format, -1e100, format_spec)
+                self.assertRaises(ValueError, format, 1e-100, format_spec)
+                self.assertRaises(ValueError, format, -1e-100, format_spec)
+
+
 def test_main():
     run_unittest(TypesTests)
 
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index ef6a722..26a57cc 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -825,6 +825,268 @@ class UnicodeTest(
             return
         self.assertRaises(OverflowError, u't\tt\t'.expandtabs, sys.maxint)
 
+    def test__format__(self):
+        def test(value, format, expected):
+            # test both with and without the trailing 's'
+            self.assertEqual(value.__format__(format), expected)
+            self.assertEqual(value.__format__(format + u's'), expected)
+
+        test(u'', u'', u'')
+        test(u'abc', u'', u'abc')
+        test(u'abc', u'.3', u'abc')
+        test(u'ab', u'.3', u'ab')
+        test(u'abcdef', u'.3', u'abc')
+        test(u'abcdef', u'.0', u'')
+        test(u'abc', u'3.3', u'abc')
+        test(u'abc', u'2.3', u'abc')
+        test(u'abc', u'2.2', u'ab')
+        test(u'abc', u'3.2', u'ab ')
+        test(u'result', u'x<0', u'result')
+        test(u'result', u'x<5', u'result')
+        test(u'result', u'x<6', u'result')
+        test(u'result', u'x<7', u'resultx')
+        test(u'result', u'x<8', u'resultxx')
+        test(u'result', u' <7', u'result ')
+        test(u'result', u'<7', u'result ')
+        test(u'result', u'>7', u' result')
+        test(u'result', u'>8', u'  result')
+        test(u'result', u'^8', u' result ')
+        test(u'result', u'^9', u' result  ')
+        test(u'result', u'^10', u'  result  ')
+        test(u'a', u'10000', u'a' + u' ' * 9999)
+        test(u'', u'10000', u' ' * 10000)
+        test(u'', u'10000000', u' ' * 10000000)
+
+        # test mixing unicode and str
+        self.assertEqual(u'abc'.__format__('s'), u'abc')
+        self.assertEqual(u'abc'.__format__('->10s'), u'-------abc')
+
+    def test_format(self):
+        self.assertEqual(u''.format(), u'')
+        self.assertEqual(u'a'.format(), u'a')
+        self.assertEqual(u'ab'.format(), u'ab')
+        self.assertEqual(u'a{{'.format(), u'a{')
+        self.assertEqual(u'a}}'.format(), u'a}')
+        self.assertEqual(u'{{b'.format(), u'{b')
+        self.assertEqual(u'}}b'.format(), u'}b')
+        self.assertEqual(u'a{{b'.format(), u'a{b')
+
+        # examples from the PEP:
+        import datetime
+        self.assertEqual(u"My name is {0}".format(u'Fred'), u"My name is Fred")
+        self.assertEqual(u"My name is {0[name]}".format(dict(name=u'Fred')),
+                         u"My name is Fred")
+        self.assertEqual(u"My name is {0} :-{{}}".format(u'Fred'),
+                         u"My name is Fred :-{}")
+
+        # datetime.__format__ doesn't work with unicode
+        #d = datetime.date(2007, 8, 18)
+        #self.assertEqual("The year is {0.year}".format(d),
+        #                 "The year is 2007")
+
+        # classes we'll use for testing
+        class C:
+            def __init__(self, x=100):
+                self._x = x
+            def __format__(self, spec):
+                return spec
+
+        class D:
+            def __init__(self, x):
+                self.x = x
+            def __format__(self, spec):
+                return str(self.x)
+
+        # class with __str__, but no __format__
+        class E:
+            def __init__(self, x):
+                self.x = x
+            def __str__(self):
+                return u'E(' + self.x + u')'
+
+        # class with __repr__, but no __format__ or __str__
+        class F:
+            def __init__(self, x):
+                self.x = x
+            def __repr__(self):
+                return u'F(' + self.x + u')'
+
+        # class with __format__ that forwards to string, for some format_spec's
+        class G:
+            def __init__(self, x):
+                self.x = x
+            def __str__(self):
+                return u"string is " + self.x
+            def __format__(self, format_spec):
+                if format_spec == 'd':
+                    return u'G(' + self.x + u')'
+                return object.__format__(self, format_spec)
+
+        # class that returns a bad type from __format__
+        class H:
+            def __format__(self, format_spec):
+                return 1.0
+
+        class I(datetime.date):
+            def __format__(self, format_spec):
+                return self.strftime(format_spec)
+
+        class J(int):
+            def __format__(self, format_spec):
+                return int.__format__(self * 2, format_spec)
+
+
+        self.assertEqual(u''.format(), u'')
+        self.assertEqual(u'abc'.format(), u'abc')
+        self.assertEqual(u'{0}'.format(u'abc'), u'abc')
+        self.assertEqual(u'{0:}'.format(u'abc'), u'abc')
+        self.assertEqual(u'X{0}'.format(u'abc'), u'Xabc')
+        self.assertEqual(u'{0}X'.format(u'abc'), u'abcX')
+        self.assertEqual(u'X{0}Y'.format(u'abc'), u'XabcY')
+        self.assertEqual(u'{1}'.format(1, u'abc'), u'abc')
+        self.assertEqual(u'X{1}'.format(1, u'abc'), u'Xabc')
+        self.assertEqual(u'{1}X'.format(1, u'abc'), u'abcX')
+        self.assertEqual(u'X{1}Y'.format(1, u'abc'), u'XabcY')
+        self.assertEqual(u'{0}'.format(-15), u'-15')
+        self.assertEqual(u'{0}{1}'.format(-15, u'abc'), u'-15abc')
+        self.assertEqual(u'{0}X{1}'.format(-15, u'abc'), u'-15Xabc')
+        self.assertEqual(u'{{'.format(), u'{')
+        self.assertEqual(u'}}'.format(), u'}')
+        self.assertEqual(u'{{}}'.format(), u'{}')
+        self.assertEqual(u'{{x}}'.format(), u'{x}')
+        self.assertEqual(u'{{{0}}}'.format(123), u'{123}')
+        self.assertEqual(u'{{{{0}}}}'.format(), u'{{0}}')
+        self.assertEqual(u'}}{{'.format(), u'}{')
+        self.assertEqual(u'}}x{{'.format(), u'}x{')
+
+        # weird field names
+        self.assertEqual(u"{0[foo-bar]}".format({u'foo-bar':u'baz'}), u'baz')
+        self.assertEqual(u"{0[foo bar]}".format({u'foo bar':u'baz'}), u'baz')
+        self.assertEqual(u"{0[ ]}".format({u' ':3}), u'3')
+
+        self.assertEqual(u'{foo._x}'.format(foo=C(20)), u'20')
+        self.assertEqual(u'{1}{0}'.format(D(10), D(20)), u'2010')
+        self.assertEqual(u'{0._x.x}'.format(C(D(u'abc'))), u'abc')
+        self.assertEqual(u'{0[0]}'.format([u'abc', u'def']), u'abc')
+        self.assertEqual(u'{0[1]}'.format([u'abc', u'def']), u'def')
+        self.assertEqual(u'{0[1][0]}'.format([u'abc', [u'def']]), u'def')
+        self.assertEqual(u'{0[1][0].x}'.format(['abc', [D(u'def')]]), u'def')
+
+        # strings
+        self.assertEqual(u'{0:.3s}'.format(u'abc'), u'abc')
+        self.assertEqual(u'{0:.3s}'.format(u'ab'), u'ab')
+        self.assertEqual(u'{0:.3s}'.format(u'abcdef'), u'abc')
+        self.assertEqual(u'{0:.0s}'.format(u'abcdef'), u'')
+        self.assertEqual(u'{0:3.3s}'.format(u'abc'), u'abc')
+        self.assertEqual(u'{0:2.3s}'.format(u'abc'), u'abc')
+        self.assertEqual(u'{0:2.2s}'.format(u'abc'), u'ab')
+        self.assertEqual(u'{0:3.2s}'.format(u'abc'), u'ab ')
+        self.assertEqual(u'{0:x<0s}'.format(u'result'), u'result')
+        self.assertEqual(u'{0:x<5s}'.format(u'result'), u'result')
+        self.assertEqual(u'{0:x<6s}'.format(u'result'), u'result')
+        self.assertEqual(u'{0:x<7s}'.format(u'result'), u'resultx')
+        self.assertEqual(u'{0:x<8s}'.format(u'result'), u'resultxx')
+        self.assertEqual(u'{0: <7s}'.format(u'result'), u'result ')
+        self.assertEqual(u'{0:<7s}'.format(u'result'), u'result ')
+        self.assertEqual(u'{0:>7s}'.format(u'result'), u' result')
+        self.assertEqual(u'{0:>8s}'.format(u'result'), u'  result')
+        self.assertEqual(u'{0:^8s}'.format(u'result'), u' result ')
+        self.assertEqual(u'{0:^9s}'.format(u'result'), u' result  ')
+        self.assertEqual(u'{0:^10s}'.format(u'result'), u'  result  ')
+        self.assertEqual(u'{0:10000}'.format(u'a'), u'a' + u' ' * 9999)
+        self.assertEqual(u'{0:10000}'.format(u''), u' ' * 10000)
+        self.assertEqual(u'{0:10000000}'.format(u''), u' ' * 10000000)
+
+        # format specifiers for user defined type
+        self.assertEqual(u'{0:abc}'.format(C()), u'abc')
+
+        # !r and !s coersions
+        self.assertEqual(u'{0!s}'.format(u'Hello'), u'Hello')
+        self.assertEqual(u'{0!s:}'.format(u'Hello'), u'Hello')
+        self.assertEqual(u'{0!s:15}'.format(u'Hello'), u'Hello          ')
+        self.assertEqual(u'{0!s:15s}'.format(u'Hello'), u'Hello          ')
+        self.assertEqual(u'{0!r}'.format(u'Hello'), u"u'Hello'")
+        self.assertEqual(u'{0!r:}'.format(u'Hello'), u"u'Hello'")
+        self.assertEqual(u'{0!r}'.format(F(u'Hello')), u'F(Hello)')
+
+        # test fallback to object.__format__
+        self.assertEqual(u'{0}'.format({}), u'{}')
+        self.assertEqual(u'{0}'.format([]), u'[]')
+        self.assertEqual(u'{0}'.format([1]), u'[1]')
+        self.assertEqual(u'{0}'.format(E(u'data')), u'E(data)')
+        self.assertEqual(u'{0:^10}'.format(E(u'data')), u' E(data)  ')
+        self.assertEqual(u'{0:^10s}'.format(E(u'data')), u' E(data)  ')
+        self.assertEqual(u'{0:d}'.format(G(u'data')), u'G(data)')
+        self.assertEqual(u'{0:>15s}'.format(G(u'data')), u' string is data')
+        self.assertEqual(u'{0!s}'.format(G(u'data')), u'string is data')
+
+        self.assertEqual("{0:date: %Y-%m-%d}".format(I(year=2007,
+                                                       month=8,
+                                                       day=27)),
+                         "date: 2007-08-27")
+
+        # test deriving from a builtin type and overriding __format__
+        self.assertEqual("{0}".format(J(10)), "20")
+
+
+        # string format specifiers
+        self.assertEqual('{0:}'.format('a'), 'a')
+
+        # computed format specifiers
+        self.assertEqual("{0:.{1}}".format('hello world', 5), 'hello')
+        self.assertEqual("{0:.{1}s}".format('hello world', 5), 'hello')
+        self.assertEqual("{0:.{precision}s}".format('hello world', precision=5), 'hello')
+        self.assertEqual("{0:{width}.{precision}s}".format('hello world', width=10, precision=5), 'hello     ')
+        self.assertEqual("{0:{width}.{precision}s}".format('hello world', width='10', precision='5'), 'hello     ')
+
+        # test various errors
+        self.assertRaises(ValueError, '{'.format)
+        self.assertRaises(ValueError, '}'.format)
+        self.assertRaises(ValueError, 'a{'.format)
+        self.assertRaises(ValueError, 'a}'.format)
+        self.assertRaises(ValueError, '{a'.format)
+        self.assertRaises(ValueError, '}a'.format)
+        self.assertRaises(IndexError, '{0}'.format)
+        self.assertRaises(IndexError, '{1}'.format, 'abc')
+        self.assertRaises(KeyError,   '{x}'.format)
+        self.assertRaises(ValueError, "}{".format)
+        self.assertRaises(ValueError, "{".format)
+        self.assertRaises(ValueError, "}".format)
+        self.assertRaises(ValueError, "abc{0:{}".format)
+        self.assertRaises(ValueError, "{0".format)
+        self.assertRaises(IndexError, "{0.}".format)
+        self.assertRaises(ValueError, "{0.}".format, 0)
+        self.assertRaises(IndexError, "{0[}".format)
+        self.assertRaises(ValueError, "{0[}".format, [])
+        self.assertRaises(KeyError,   "{0]}".format)
+        self.assertRaises(ValueError, "{0.[]}".format, 0)
+        self.assertRaises(ValueError, "{0..foo}".format, 0)
+        self.assertRaises(ValueError, "{0[0}".format, 0)
+        self.assertRaises(ValueError, "{0[0:foo}".format, 0)
+        self.assertRaises(KeyError,   "{c]}".format)
+        self.assertRaises(ValueError, "{{ {{{0}}".format, 0)
+        self.assertRaises(ValueError, "{0}}".format, 0)
+        self.assertRaises(KeyError,   "{foo}".format, bar=3)
+        self.assertRaises(ValueError, "{0!x}".format, 3)
+        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)
+
+        # can't have a replacement on the field name portion
+        self.assertRaises(TypeError, '{0[{1}]}'.format, 'abcdefg', 4)
+
+        # exceed maximum recursion depth
+        self.assertRaises(ValueError, "{0:{1:{2}}}".format, 'abc', 's', '')
+        self.assertRaises(ValueError, "{0:{1:{2:{3:{4:{5:{6}}}}}}}".format,
+                          0, 1, 2, 3, 4, 5, 6, 7)
+
+        # string format spec errors
+        self.assertRaises(ValueError, "{0:-s}".format, '')
+        self.assertRaises(ValueError, format, "", "-")
+        self.assertRaises(ValueError, "{0:=s}".format, '')
 
 def test_main():
     test_support.run_unittest(__name__)