python萌新 re求助各位大神

with open("reverse.in") as file:
    n = file.readline()
    nn = int(n)
    sign = ""
    if(nn < 0):
        sign = n[0]
        n = n[1:]
    n = n[::-1]
    if(n == '0'):

pass

    else:
        t = n[0]
        while(t == '0'):
            n = n[1:]
            t = n[0]
    n = sign + n
    with open('reverse.out','w') as file2:
        file2.write(n)        
不知道为什么会re，结果的话测试过很多种都没问题 难道是打开文件的问题吗