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Created November 21, 2011 23:31
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''.format_map() in Python 2.x
"""''.format_map() in Python 2.x"""
try:
''.format_map({})
except AttributeError: # Python < 3.2
import string
def format_map(format_string, mapping, _format=string.Formatter().vformat):
return _format(format_string, None, mapping)
del string
#XXX works on CPython 2.6
# http://stackoverflow.com/questions/2444680/how-do-i-add-my-own-custom-attributes-to-existing-built-in-python-types-like-a/2450942#2450942
import ctypes as c
class PyObject_HEAD(c.Structure):
_fields_ = [
('HEAD', c.c_ubyte * (object.__basicsize__ - c.sizeof(c.c_void_p))),
('ob_type', c.c_void_p)
]
_get_dict = c.pythonapi._PyObject_GetDictPtr
_get_dict.restype = c.POINTER(c.py_object)
_get_dict.argtypes = [c.py_object]
def get_dict(object):
return _get_dict(object).contents.value
get_dict(str)['format_map'] = format_map
else: # Python 3.2+
def format_map(format_string, mapping):
return format_string.format_map(mapping)
# test
import unittest
class FormatMapTestCase(unittest.TestCase):
def test_format_map(self):
self._test_format_map(lambda s, *args: s.format_map(*args))
def test_function_format_map(self):
self._test_format_map(format_map)
def _test_format_map(self, format_map):
# taken from Python source code
self.assertEqual(format_map('', {}), '')
self.assertEqual(format_map('a', {}), 'a')
self.assertEqual(format_map('ab', {}), 'ab')
self.assertEqual(format_map('a{{', {}), 'a{')
self.assertEqual(format_map('a}}', {}), 'a}')
self.assertEqual(format_map('{{b', {}), '{b')
self.assertEqual(format_map('}}b', {}), '}b')
self.assertEqual(format_map('a{{b', {}), 'a{b')
# using mappings
class Mapping(dict):
def __missing__(self, key):
return key
self.assertEqual(format_map('{hello}', Mapping()), 'hello')
self.assertEqual(format_map('{a} {world}', Mapping(a='hello')), 'hello world')
class InternalMapping:
def __init__(self):
self.mapping = {'a': 'hello'}
def __getitem__(self, key):
return self.mapping[key]
self.assertEqual(format_map('{a}', InternalMapping()), 'hello')
class C:
def __init__(self, x=100):
self._x = x
def __format__(self, spec):
return spec
self.assertEqual(format_map('{foo._x}', {'foo': C(20)}), '20')
# test various errors
self.assertRaises(TypeError, format_map, '{')
self.assertRaises(TypeError, format_map, '}')
self.assertRaises(TypeError, format_map, 'a{')
self.assertRaises(TypeError, format_map, 'a}')
self.assertRaises(TypeError, format_map, '{a')
self.assertRaises(TypeError, format_map, '}a')
self.assertRaises(ValueError, format_map, '{', {})
self.assertRaises(ValueError, format_map, '}', {})
self.assertRaises(ValueError, format_map, 'a{', {})
self.assertRaises(ValueError, format_map, 'a}', {})
self.assertRaises(ValueError, format_map, '{a', {})
self.assertRaises(ValueError, format_map, '}a', {})
# issue #12579: can't supply positional params to format_map
self.assertRaises(ValueError, format_map, '{}', {'a' : 2})
self.assertRaises(ValueError, format_map, '{}', 'a')
self.assertRaises(ValueError, format_map, '{a} {}', {"a" : 2, "b" : 1})
if __name__=="__main__":
unittest.main()
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