题解 | #整数与IP地址间的转换#Python：进制转换

import sys

def int2bin(num: str) -> str:  # 将十进制字符串 num 转化为二进制字符串
    num = int(num)
    bin_num = list()
    base = 2
    while num > 0:
        digit = num % base
        bin_num.append(str(digit))
        num = num // base
    bin_num = bin_num[::-1]
    return ''.join(bin_num)

for line in sys.stdin:
    if len(list(line.strip().split("."))) < 4:  # 十进制 to IP
        num = line.strip()
        bin_str = int2bin(num).zfill(32)
        ans = [str(int(''.join(bin_str[8*i:8*(i+1)]), 2)) for i in range(4)]
        print('.'.join(ans))
    else:  # IP to 十进制
        IP_list = list(line.strip().split('.'))  # ['10', '0', '3', '193']
        int_num = int(''.join([int2bin(x).zfill(8) for x in IP_list]), 2)
        print(str(int_num))