String Multiply without Multiplying

2020-12-07.py

import re
from itertools import cycle, islice

question = """

Given two non-negative integers n1 and n2 represented as strings, 
return the product of n1 and n2, also represented as a string. 
Neither input will start with 0, and don’t just convert it to an 
integer and do the math that way.


Examples:
$ stringMultiply(“123”, “456”)
$ “56088”

"""

def stringMultiple(a, b):
    a1 = [char for char in a]
    b1 = [char for char in b]
    c = [[ 0 for x in range(0, len(a1))] for y in range(0, len(b1))]
    w = [[] for x in range(0, len(a1) + len(b1))]
    for a2 in range(0, len(a1)):
        for b2 in range(0, len(b1)):
            cprod = str(eval('+'.join(islice(cycle(a1[a2]), (ord(b1[b2])-48)))))
            cprod = '0' + cprod if len(cprod) == 1 else cprod
            c[a2][b2] = cprod
            c2 = a2 + b2 + 1
            w[c2].append([a2,b2])

    carry = 0
    w1 = [ [] for x in range(0, len(w)) ]
    for w2 in reversed(range(0,len(w))):
        w3 = 0
        if w2 == len(w) - 1:
            for w4 in w[w2]:
                a3, b3 = w4
                w1[w2] = [char for char in c[a3][b3]][1]
                carry = '0'
        else:
            w5 = []
            for w4 in w[w2]:
                a3, b3 = w4
                w1[w2].append([char for char in c[a3][b3]][1])
            for w5 in w[w2 + 1]:
                a3, b3 = w5
                w1[w2].append([char for char in c[a3][b3]][0])
            w1[w2].append(carry)
            w6 = str(eval('+'.join(w1[w2])))
            w6 = '0' + w6 if len(w6) == 1 else w6
            carry = [char for char in w6][0]
            y = [char for char in w6][1]
            w1[w2] = y

    wz = re.sub(r'^0', '', ''.join(w1))
    return wz

print(stringMultiple("123", "456"))