class NamedTuple(tuple):
"""Builds a tuple with elements named and indexed.
A NamedTuple is constructed with a sequence of (name, value) pairs;
the values can then be obtained by looking up the name or the value.
"""
def __new__(cls, seq):
return tuple.__new__(cls, [val for name,val in seq])
def __init__(self, seq):
tuple.__init__(self)
tuple.__setattr__(self, "_names", dict(zip([name for name,val in seq], range(len(seq)))))
def __getattr__(self, name):
try:
return tuple.__getitem__(self, self.__dict__["_names"][name])
except KeyError:
raise AttributeError, "object has no attribute named '%s'" % name
def __setattr__(self, name, value):
raise TypeError, "'NamedTuple' object has only read-only attributes (assign to .%s)" % name
