[Python知识库]1001 A+B Format (20分) python

1001 A+B Format (20 分)

Calculate a+b and output the sum in standard format – that is, the digits must be separated into groups of three by commas (unless there are less than four digits).

Input Specification:

Each input file contains one test case. Each case contains a pair of integers a and b where ?10^6 ≤
a,b≤10^6. The numbers are separated by a space.

Output Specification:

For each test case, you should output the sum of a and b in one line. The sum must be written in the standard format.

Sample Input:

-1000000 9

Sample Output:

-999,991

a, b = map(int, input().split(' '))
c = list(str(a + b))
n = 0
# 从后往前遍历
for i in range(len(c) - 1, -1, -1):
    n += 1
    # 从后往前数的每第三个字符，且这个字符不能为加法结果中的第一个数字或负号，它的前面也不能是负号
    if n % 3 == 0 and i != 0 and c[i-1] != '-':
        c.insert(i, ',')
print(''.join(c))