正則表達式是Python程序設計中非常實用的功能，本文就常用的正則表達式做一匯總，供大家參考之用。具體如下：
一、字符串替換
1.替換所有匹配的子串
用newstring替換subject中所有與正則表達式regex匹配的子串
result, number = re.subn(regex, newstring, subject)
2.替換所有匹配的子串（使用正則表達式對象）
reobj = re.compile(regex)
result, number = reobj.subn(newstring, subject)
二、字符串拆分
1.字符串拆分
result = re.split(regex, subject)
2.字符串拆分（使用正則表示式對象）
reobj = re.compile(regex)
result = reobj.split(subject)
三、匹配
下面列出Python正則表達式的幾種匹配用法：
1.測試正則表達式是否匹配字符串的全部或部分
regex=ur"..." #正則表達式
if re.search(regex, subject):
do_something()
else:
do_anotherthing()
2.測試正則表達式是否匹配整個字符串
regex=ur"...\Z" #正則表達式末尾以\Z結束
if re.match(regex, subject):
do_something()
else:
do_anotherthing()
3. 創建一個匹配對象，然后通過該對象獲得匹配細節
regex=ur"..." #正則表達式
match = re.search(regex, subject)
if match:
# match start: match.start()
# match end (exclusive): match.end()
# matched text: match.group()
do_something()
else:
do_anotherthing()
4.獲取正則表達式所匹配的子串
(Get the part of a string matched by the regex)
regex=ur"..." #正則表達式
match = re.search(regex, subject)
if match:
result = match.group()
else:
result = ""
5. 獲取捕獲組所匹配的子串
(Get the part of a string matched by a capturing group)
regex=ur"..." #正則表達式
match = re.search(regex, subject)
if match:
result = match.group(1)
else:
result = ""
6. 獲取有名組所匹配的子串
(Get the part of a string matched by a named group)
regex=ur"..." #正則表達式
match = re.search(regex, subject)
if match:
result = match.group("groupname")
else:
result = ""
7. 將字符串中所有匹配的子串放入數組中
(Get an array of all regex matches in a string)
result = re.findall(regex, subject)
8.遍歷所有匹配的子串
(Iterate over all matches in a string)
for match in re.finditer(r"<(.*?)\s*.*?/\1>", subject)
# match start: match.start()
# match end (exclusive): match.end()
# matched text: match.group()
9.通過正則表達式字符串創建一個正則表達式對象
(Create an object to use the same regex for many operations)
reobj = re.compile(regex)
10.用法１的正則表達式對象版本
(use regex object for if/else branch whether (part of) a string can be matched)
reobj = re.compile(regex)
if reobj.search(subject):
do_something()
else:
do_anotherthing()
11.用法２的正則表達式對象版本
(use regex object for if/else branch whether a string can be matched entirely)
reobj = re.compile(r"\Z") #正則表達式末尾以\Z 結束
if reobj.match(subject):
do_something()
else:
do_anotherthing()
12.創建一個正則表達式對象，然后通過該對象獲得匹配細節
(Create an object with details about how the regex object matches (part of) a string)
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
# match start: match.start()
# match end (exclusive): match.end()
# matched text: match.group()
do_something()
else:
do_anotherthing()
13.用正則表達式對象獲取匹配子串
(Use regex object to get the part of a string matched by the regex)
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
result = match.group()
else:
result = ""
14.用正則表達式對象獲取捕獲組所匹配的子串
(Use regex object to get the part of a string matched by a capturing group)
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
result = match.group(1)
else:
result = ""
15.用正則表達式對象獲取有名組所匹配的子串
(Use regex object to get the part of a string matched by a named group)
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
result = match.group("groupname")
else:
result = ""
16.用正則表達式對象獲取所有匹配子串并放入數組
(Use regex object to get an array of all regex matches in a string)
reobj = re.compile(regex)
result = reobj.findall(subject)
17.通過正則表達式對象遍歷所有匹配子串
(Use regex object to iterate over all matches in a string)
reobj = re.compile(regex)
for match in reobj.finditer(subject):
# match start: match.start()
# match end (exclusive): match.end()
# matched text: match.group()
感興趣的讀者可以動手調試一下本文實例代碼，相信會有新的收獲。
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