请实现一个函数，将一个字符串中的每个空格替换成"20%"。例如，当字符串为We Are Happy. 则经过替换之后的字符串为We20%Are20%Happy.
class Solution:
def replaceSpace(self, s):
strLen = len(s)
aaa = []
for i in range(0, strLen):
if s[i] == " ":
aaa.append("20%")
else:
aaa.append(s[i])
return ''.join(aaa)
if __name__ == '__main__':
s = Solution()
print(s.replaceSpace("We Are Happy "))
运行结果为：
We20%Are20%Happy20%