63 lines
2.2 KiB
Python
63 lines
2.2 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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"""
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field_names = s.split()
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nargs = len(field_names)
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def __new__(cls, *args, **kwds):
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if kwds:
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try:
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args += tuple(kwds[name] for name in field_names[len(args):])
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except KeyError, name:
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raise TypeError('%s missing required argument: %s' % (typename, name))
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if len(args) != nargs:
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raise TypeError('%s takes exactly %d arguments (%d given)' % (typename, nargs, len(args)))
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return tuple.__new__(cls, args)
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repr_template = '%s(%s)' % (typename, ', '.join('%s=%%r' % name for name in field_names))
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m = dict(vars(tuple)) # pre-lookup superclass methods (for faster lookup)
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m.update(__doc__= '%s(%s)' % (typename, ', '.join(field_names)),
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__slots__ = (), # no per-instance dict (so instances are same size as tuples)
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__new__ = __new__,
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__repr__ = lambda self, _format=repr_template.__mod__: _format(self),
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__module__ = _sys._getframe(1).f_globals['__name__'],
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)
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m.update((name, property(_itemgetter(index))) for index, name in enumerate(field_names))
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return type(typename, (tuple,), m)
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if __name__ == '__main__':
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# verify that instances are pickable
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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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