reduce and partial in Python

Two functools staples: folding and pre-filling arguments.

from functools import reduce, partial

product = reduce(lambda acc, n: acc * n, [1, 2, 3, 4], 1)
running = reduce(lambda acc, n: acc + [acc[-1] + n], [1, 2, 3], [0])


def power(base, exponent):
    return base ** exponent


square = partial(power, exponent=2)
cube = partial(power, exponent=3)
nine = square(3)

How it works

1. reduce folds a sequence into one value.
2. partial fixes an argument to make a new function.
3. square and cube specialize one power.

Keywords and builtins used here

• def
• lambda
• power
• return

The run, in numbers

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Step 5 of 5 in Generators & itertools, step 14 of 53 in Pythonic Python.

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