Python's standard library is vast, and my intuition tells that there must be a way in it to accomplish this, but I just can't figure it out. This is purely for curiosity and learning purposes: I have two simple functions: def increment(x): return x + 1 def double(x): return x * 2 and I want to compose them into a new function double_and_increment. I could of course simply do that as such: double_and_increment = lambda x: increment(double(x)) but I could also do it in a more convoluted but perhaps more "ergonomically scalable" way: import functools double_and_increment = functools.partial(functools.reduce, lambda acc, f: f(acc), [double, increment]) Both of the above work fine: >>> double_and_increment(1) 3 Now, the question is, is there tooling in the standard library that would allow achieving the composition without any user-defined lambdas, regular functions, or classes. The first intuition is to replace the lambda acc, f: f(acc) definition in the functools.reduce call with operator.call, but that unfortunately takes the arguments in the reverse order: >>> (lambda acc, f: f(acc))(1, str) # What we want to replace. >>> '1' >>> import operator >>> operator.call(str, 1) # Incorrect argument order. >>> '1' I have a hunch that using functools.reduce is still the way to accomplish the composition, but for the life of me I can't figure out a way to get rid of the user-defined lambda. Few out-of-the-box methods that got me close: import functools, operator # Curried form, can't figure out how to uncurry. functools.partial(operator.methodcaller, '__call__')(1)(str) # The arguments needs to be in the middle of the expression, which does not work. operator.call(*reversed(operator.attrgetter('args')(functools.partial(functools.partial, operator.call)(1, str)))) Have looked through all the existing questions, but they are completely different and rely on using user-defined functions and/or lambdas. Continue reading...
