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楼主您好，请问一下, 比如把一个字符串strs = “it is a good job. he is very happy” 用 re.sub(“(it) is”,”\1’s”,strs),可以得到”it’s a good job. he is very happy“。同样我使用re.sub(“(it|he) is”,”\1’s”,strs),不能同时替换两个（it is, he is）->(it’s, he’s)，如有可以的话，请问怎么写?
答：
去试了：
import re
inputStr = "it is a good job. he is very happy"
replacedStr = re.sub("(it) is", "\1’s", inputStr)
print("replacedStr=%s" % replacedStr)-》 并没有得到：it’s a good job. he is very happy
只有：
replacedStr=’s a good job. he is very happy
参考自己的教程中的：
inputStr = "hello crifan, nihao crifan" replacedStr = re.sub(r"hello (\w+), nihao \1", "\g<1>", inputStr) print "replacedStr=",replacedStr; #crifan
改为：
\g<1>
的写法：
replacedStrWithG = re.sub("(it) is", "\g<1>’s", inputStr)
print("replacedStrWithG=%s" % replacedStrWithG)才可以得到
replacedStrWithG=it’s a good job. he is very happy
后面也是类似的逻辑：
replaceAllStr = re.sub("(it|he) is", "\1’s", inputStr)
print("replaceAllStr=%s" % replaceAllStr)只能得到：
replaceAllStr=’s a good job. ’s very happy
replaceAllStrWithG = re.sub("(it|he) is", "\g<1>’s", inputStr)
print("replaceAllStrWithG=%s" % replaceAllStrWithG)才能得到：
replaceAllStrWithG=it’s a good job. he’s very happy
之前此人错误的原因：
把 当前要被替换的字符串中的 \1，放到了 被替换后的字符串中了
我之前的例子：
inputStr = "hello crifan, nihao crifan"
想要匹配到：
hello xxx, nihao xxx
中的第二个xxx，确保和第一个一样，才会用：
"hello (\w+), nihao \1"
而，re.sub的替换后的结果中，要去引用，被替换中的组=group，要加上
\g<N>
N =1,2,3。。。
具体写法
replacedStr = re.sub(r"hello (\w+), nihao \1", "\g<1>", inputStr)
或用命名的组：
inputStr = "hello crifan, nihao crifan" replacedStr = re.sub(r"hello (?P<name>\w+), nihao (?P=name)", "\g<name>", inputStr)
此处例子中的写法是：
replaceAllStrNamedGroup = re.sub("(?P<hostPart>it|he) is", "\g<hostPart>’s", inputStr)
print("replaceAllStrNamedGroup=%s" % replaceAllStrNamedGroup)同样可以得到我们要的：
replaceAllStrNamedGroup=it’s a good job. he’s very happy
完整代码：
# Function: re.sub not match all, comment on https://www.crifan.com/python_re_sub_detailed_introduction/
# Author: Crifan Li
# Update: 20210816
import re
inputStr = "it is a good job. he is very happy"
replacedStr = re.sub("(it) is", "\1’s", inputStr)
print("replacedStr=%s" % replacedStr)
# replacedStr=’s a good job. he is very happy
# -》 并没有得到：it’s a good job. he is very happy
replacedStrWithG = re.sub("(it) is", "\g<1>’s", inputStr)
print("replacedStrWithG=%s" % replacedStrWithG)
# replacedStrWithG=it’s a good job. he is very happy
replaceAllStr = re.sub("(it|he) is", "\1’s", inputStr)
print("replaceAllStr=%s" % replaceAllStr)
# replaceAllStr=’s a good job. ’s very happy
replaceAllStrWithG = re.sub("(it|he) is", "\g<1>’s", inputStr)
print("replaceAllStrWithG=%s" % replaceAllStrWithG)
# replaceAllStrWithG=it’s a good job. he’s very happy
replaceAllStrNamedGroup = re.sub("(?P<hostPart>it|he) is", "\g<hostPart>’s", inputStr)
print("replaceAllStrNamedGroup=%s" % replaceAllStrNamedGroup)
# replaceAllStrNamedGroup=it’s a good job. he’s very happy转载请注明：在路上 » 【问题解答】正则re.sub匹配不到全部的组的内容