persistence.py

def persistence(n):
    p = 0
    while n > 9:
        d, n = n, 1
        while d:
            d, m = divmod(d, 10)
            n *= m
        p += 1
    return p


from functools import reduce
from operator import mul

def persistence_(n):
    p = 0
    while n > 9:
        n = reduce(mul, map(int, str(n)))
        p += 1
    return p


def persistence__(n):
    p = 0
    while n > 9:
        n = reduce((lambda x, y: x * y), map(int, str(n)))
        p += 1
    return p