[Python-Dev] functools additions (original) (raw)

SevenInchBread adamadamadamamiadam at gmail.com
Sun Apr 15 12:38:43 CEST 2007

So.... if it's alright with the privledged folk - I'd like to commit these minor (and probably non-controversial) additions to the functools module.

def cat(x): return x

def multimap(func, s, n=2): assert n > 0, "n must be positive" return (map(func, seq) if n == 1 else map(lambda x: multimap(func, x, n-1), seq))

def multifilter(func, s, n=2): return multimap(lambda x: filter(func, x), s, n-1)

def multireduce(func, s, n=2): return multimap(lambda x: reduce(func, x), s, n-1)

class nullfunc(object): def call(self, *a, **k): return self def __getattr(self, name): return getattr(None, name)

cat is a generic identity function - useful for some higher-order functions to specify a function that "does nothing". multimap, multifilter, and multireduce, are all multi-dimensional versions of map, filter, and reduce. nullfunc is a special callable object that emulates the failed callable None proposal - which wasn't really a good idea, but would have been more useful as a different object apart from None.

you could probably even put cat in builtins - so you don't need to waste effort importing such a trivial function.

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