mirror of https://github.com/python/cpython
72 lines
2.6 KiB
Python
72 lines
2.6 KiB
Python
__all__ = ['deque', 'defaultdict', 'NamedTuple']
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from _collections import deque, defaultdict
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from operator import itemgetter as _itemgetter
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import sys as _sys
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def NamedTuple(typename, s):
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"""Returns a new subclass of tuple with named fields.
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>>> Point = NamedTuple('Point', 'x y')
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>>> Point.__doc__ # docstring for the new class
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'Point(x, y)'
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>>> p = Point(11, y=22) # instantiate with positional args or keywords
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>>> p[0] + p[1] # works just like the tuple (11, 22)
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33
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>>> x, y = p # unpacks just like a tuple
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>>> x, y
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(11, 22)
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>>> p.x + p.y # fields also accessable by name
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33
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>>> p # readable __repr__ with name=value style
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Point(x=11, y=22)
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>>> p.__replace__('x', 100) # __replace__() is like str.replace() but targets a named field
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Point(x=100, y=22)
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>>> d = dict(zip(p.__fields__, p)) # use __fields__ to make a dictionary
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>>> d['x']
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11
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"""
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field_names = tuple(s.replace(',', ' ').split()) # names separated by spaces and/or commas
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if not ''.join((typename,) + field_names).replace('_', '').isalnum():
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raise ValueError('Type names and field names can only contain alphanumeric characters and underscores')
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argtxt = ', '.join(field_names)
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reprtxt = ', '.join('%s=%%r' % name for name in field_names)
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template = '''class %(typename)s(tuple):
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'%(typename)s(%(argtxt)s)'
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__slots__ = ()
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__fields__ = %(field_names)r
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def __new__(cls, %(argtxt)s):
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return tuple.__new__(cls, (%(argtxt)s,))
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def __repr__(self):
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return '%(typename)s(%(reprtxt)s)' %% self
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def __replace__(self, field, value):
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'Return a new %(typename)s object replacing one field with a new value'
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return %(typename)s(**dict(zip(%(field_names)r, self) + [(field, value)]))
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''' % locals()
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for i, name in enumerate(field_names):
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template += '\n %s = property(itemgetter(%d))\n' % (name, i)
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m = dict(itemgetter=_itemgetter)
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exec template in m
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result = m[typename]
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if hasattr(_sys, '_getframe'):
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result.__module__ = _sys._getframe(1).f_globals['__name__']
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return result
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if __name__ == '__main__':
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# verify that instances can be pickled
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from cPickle import loads, dumps
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Point = NamedTuple('Point', 'x, y')
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p = Point(x=10, y=20)
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assert p == loads(dumps(p))
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import doctest
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TestResults = NamedTuple('TestResults', 'failed attempted')
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print TestResults(*doctest.testmod())
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