Function Composition in Python

compose.py

import functools
from typing import Callable


def compose(*functions: Callable) -> Callable:
    return functools.reduce(lambda f, g: lambda x: g(f(x)), functions)


def add_four(x):
    return x + 4


def multiply_by_three(x):
    return x * 3


def main():
    x = 7
    f = compose(
        add_four,
        multiply_by_three,
        multiply_by_three,
        add_four,
    )
    result = f(x)
    print(f"Result: {result}")  # 103


main()