Python 的字符串转int

用惯了php的intval函数，实在不习惯python的各种报错，干脆自己实现了一下

def str2int(s):
    try:
        return int(s)
    except:
        if('-'==s[0]):
            return 0 - str2int(s[1:])
        elif s[0] in ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']:
            num = 0
            for i in range(len(s) ):
                if s[i] in ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']:
                    num = num * 10 + int(s[i])
                else:
                    return num
        else:
            return 0