Python大学编程问题(逆位序)

输入一个正整数，输出按逆位序的数字。
注意:当输出的数字含有结尾的0时，输出不应该带有前导的0，例如输入6500，输出56。输入也可能是负数

a = input()
a = a[::-1]
for i in range(len(a)):
    if a[i]!="0":
        b = a[i:]
        break
print(eval(b))

#负数判断
a = input()
a = a[::-1]
if a[len(a)-1] == "+" or a[len(a)-1] == "-":
    a = a[len(a)-1] + a[0:len(a)-1]
for i in range(len(a)):
    if a[i]!="0" and a[i] != "+" and a[i] != "-":
        b = a[0] + a[i:] if a[0] == "+" or a[0] == "-" else a[i:]
        break
print(eval(b))

n = input()
n = n.rstrip('0')
if n.startswith('-'):
    print('-'+n[:0:-1])
else:
    print(n[::-1])