Add collections.NamedTuple
diff --git a/Lib/collections.py b/Lib/collections.py
index 0d9254c..6e816dc 100644
--- a/Lib/collections.py
+++ b/Lib/collections.py
@@ -1,3 +1,62 @@
-__all__ = ['deque', 'defaultdict']
+__all__ = ['deque', 'defaultdict', 'NamedTuple']
from _collections import deque, defaultdict
+from operator import itemgetter as _itemgetter
+import sys as _sys
+
+def NamedTuple(typename, s):
+ """Returns a new subclass of tuple with named fields.
+
+ >>> Point = NamedTuple('Point', 'x y')
+ >>> Point.__doc__ # docstring for the new class
+ 'Point(x, y)'
+ >>> p = Point(11, y=22) # instantiate with positional args or keywords
+ >>> p[0] + p[1] # works just like the tuple (11, 22)
+ 33
+ >>> x, y = p # unpacks just like a tuple
+ >>> x, y
+ (11, 22)
+ >>> p.x + p.y # fields also accessable by name
+ 33
+ >>> p # readable __repr__ with name=value style
+ Point(x=11, y=22)
+
+ """
+
+ field_names = s.split()
+ nargs = len(field_names)
+
+ def __new__(cls, *args, **kwds):
+ if kwds:
+ try:
+ args += tuple(kwds[name] for name in field_names[len(args):])
+ except KeyError, name:
+ raise TypeError('%s missing required argument: %s' % (typename, name))
+ if len(args) != nargs:
+ raise TypeError('%s takes exactly %d arguments (%d given)' % (typename, nargs, len(args)))
+ return tuple.__new__(cls, args)
+
+ repr_template = '%s(%s)' % (typename, ', '.join('%s=%%r' % name for name in field_names))
+
+ m = dict(vars(tuple)) # pre-lookup superclass methods (for faster lookup)
+ m.update(__doc__= '%s(%s)' % (typename, ', '.join(field_names)),
+ __slots__ = (), # no per-instance dict (so instances are same size as tuples)
+ __new__ = __new__,
+ __repr__ = lambda self, _format=repr_template.__mod__: _format(self),
+ __module__ = _sys._getframe(1).f_globals['__name__'],
+ )
+ m.update((name, property(_itemgetter(index))) for index, name in enumerate(field_names))
+
+ return type(typename, (tuple,), m)
+
+
+if __name__ == '__main__':
+ # verify that instances are pickable
+ from cPickle import loads, dumps
+ Point = NamedTuple('Point', 'x y')
+ p = Point(x=10, y=20)
+ assert p == loads(dumps(p))
+
+ import doctest
+ TestResults = NamedTuple('TestResults', 'failed attempted')
+ print TestResults(*doctest.testmod())