43. Multiply Strings leetcode python 2016 new season

Total Accepted: 51879 Total
Submissions: 231091 Difficulty: Medium

Given two numbers represented as strings, return multiplication of the numbers as a string.
Note: The numbers can be arbitrarily large and are non-negative.

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class Solution(object):
def multiply(self, num1, num2):
"""
:type num1: str
:type num2: str
:rtype: str
"""
num1_len = len(num1)
num2_len = len(num2)
arr = [0 for _ in range(num1_len + num2_len)]
num1 = num1[::-1]
num2 = num2[::-1]
result = []
for i in range(num1_len):
for j in range(num2_len):
arr[i + j] += int(num1[i]) * int(num2[j])
for arr_i in range(num1_len + num2_len):
digit = arr[arr_i] % 10
carry = arr[arr_i] / 10
if arr_i < num1_len + num2_len - 1:
arr[arr_i + 1] += carry
result.append(str(digit))
result.reverse()
while result[0] == '0' and len(result) > 1:
del result[0]
return "".join(result)