Caching a generator

Question

A recent similar question (isinstance(foo, types.GeneratorType) or inspect.isgenerator(foo)?) got me curious about how to implement this generically.

It seems like

Answer 1

Based on this comment:

my intention here is that this would only be used if the user knows he wants to iterate multiple times over the 'iterable', but doesn't know if the input is a generator or iterable. this lets you ignore that distinction, while not losing (much) performance.

This simple solution does exactly that:

def ensure_list(it):
    if isinstance(it, (list, tuple, dict)):
        return it
    else:
        return list(it)

now ensure_list(a_list) is practically a no-op - two function calls - while ensure_list(a_generator) will turn it into a list and return it, which turned out to be faster than any other approach.