Notice that I've used 'fromPairs' rather than 'fromMapping', since consistent order matters for a tuple. Comparison semantics are inherited directly from tuple, and don't care about names (they're only interested in values).
Also, it seems like there has to be a better way to do the "opposite of zip()" in fromPairs(), but I sure as hell can't think of it.
Cheers, Nick.
>>> a = named_tuple(['x', 'y'], (3, 8))
>>> a
named_tuple(['x', 'y'], (3, 8))
>>> a.x
3
>>> a.y
8
>>> str(a)
'(3, 8)'
>>> b = named_tuple.fromPairs(sorted({'x':3, 'y':8}.items()))
>>> b
named_tuple(['x', 'y'], (3, 8))
>>> b.x
3
>>> b.y
8
>>> str(b)
'(3, 8)'
>>> a == b
True
>>>And the code for the above:
class named_tuple(tuple):
def __new__(cls, names, *args):
self = tuple.__new__(cls, *args)
self._names = dict(zip(names, range(len(names))))
return self @staticmethod
def fromPairs(items):
names = [x[0] for x in items]
values = [x[1] for x in items]
return named_tuple(names, values) def __getattr__(self, attr):
if attr in self._names:
return self[self._names[attr]]
else:
return tuple.__getattr__(attr) def __repr__(self):
return "named_tuple(%s, %s)" % (str(self.names()),
str(tuple.__repr__(self))) def __str__(self):
return tuple.__repr__(self) def names(self):
return sorted(self._names.keys(), key=self._names.__getitem__)
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