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.