If the PATTERN contains parentheses, additional list elements are created from each matching substring in the delimiter.如果PATTERN里包含括号，那么每一个匹配的定界符子字符串都会作为元素加到列表中去。
Replaces each substring of this string that matches the given regular expression with the given replacement.只有两个参数，第一个参数是要进行匹配的子串，第二个是替换串。