[Python-Dev] functools.compose to chain functions together (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Mon Aug 17 02:07:50 CEST 2009

PEP 309 was written, discussed, approved, and implemented - that's how partial ended up in the stdlib.

Ok, I'm surprised that a single addition to a module needed a PEP in order to be approved.

Interestingly, here's what the summary section in PEP 309 says: « A standard library module functional should contain an implementation of partial, /and any other higher-order functions the community want/. » (emphasis mine)

I truly cannot believe that a compose function would be easier to read to the average Python programmer: if you have

def foo(data): return compose(a, b(data), c) what would you expect that to mean? Please rewrite it as a regular Python expression, preferably without looking at the patch that has been proposed first.

Ok, here's my attempt without looking at the patch:

def foo(data): def bar(*args, **kwargs): return a(b(data)(c(*args, **kwargs))) return bar

Whether or not it is easier to read to the "average Python programmer" is not that important I think. We have lots of things that certainly aren't, and yet still exist (all of the functions in the operator module, for example; or partial itself for that matter). They are there for advanced programmers.

Regards

Antoine.

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