sum_digits.py

import random
import re
import timeit
import matplotlib.pyplot as plt
from collections import Counter


def sum_digits_math(n):
    """from https://stackoverflow.com/a/14940026/674039"""
    r = 0
    while n:
        r, n = r + n % 10, n // 10
    return r


def sum_digits_str_dumb(n):
    """from OP https://stackoverflow.com/q/14939953/674039"""
    return sum(int(i) for i in str(n))


def sum_digits_re(n):
    """from https://stackoverflow.com/a/71576042/674039"""
    d = str(n)
    return sum(int(s) * re.subn(s, "", d)[1] for s in "123456789")


def sum_digits_str_fast(n):
    d = str(n)
    return sum(int(s) * d.count(s) for s in "123456789")


def sum_digits_counter(n):
    c = Counter(str(n))
    return sum(int(k) * v for k, v in c.items())


funcs = [f for name, f in locals().items() if name.startswith("sum_digits_")]
results = {f: [] for f in funcs}
for n_digits in range(1, 200):
    digits = random.choices("0123456789", k=n_digits)
    n = int("".join(digits))
    assert len({f(n) for f in funcs}) == 1
    for func in funcs:
        t = timeit.timeit(lambda: func(n), number=10)
        results[func].append(t)

for func in funcs:
    plt.plot(results[func], label=func.__name__)

plt.xlabel("len(str(n))")
plt.ylabel("t")
plt.legend()
plt.show()