offer4

# coding=utf-8def replaces1(s):    ss=''#定义一个空字符串    if type(s)!=str:        return    for i in s:            if i==' ':#i是否等于空格                ss+='%20'            else:                ss+=i    return ss#字符替换--%20-''def replaces2(s):    s= '%20'.join(s.split(' '))    return sdef replaces3(s):    s='%20'.join(s)    return sif __name__ == '__main__':    s = 'i am happy'    s2 = ['i','am','happy']    print replaces1(s)    print replaces2(s)#字符串join用法    print replaces3(s2)#序列join用法