======  Python正则表达式的用法 ======

=====  字符串替换 =====



==== 1.替换所有匹配的子串 ====

用newstring替换subject中所有与正则表达式regex匹配的子串
<code python>
result, number = re.subn(regex, newstring, subject)
</code>


==== 2.替换所有匹配的子串（使用正则表达式对象） ====
<code python>
reobj = re.compile(regex)
result, number = reobj.subn(newstring, subject)
</code>
 

===== 字符串拆分 =====

==== 1.字符串拆分 ====
<code python>
result = re.split(regex, subject)
</code>



==== 2.字符串拆分（使用正则表示式对象） ====
<code python>
reobj = re.compile(regex)
result = reobj.split(subject)
</code>

===== 匹配 =====

下面列出Python正则表达式的几种匹配用法：

==== 1.测试正则表达式是否匹配字符串的全部或部分 ====

<code python>
regex=ur"..." #正则表达式
if re.search(regex, subject):
    do_something()
else:
    do_anotherthing()
</code>


====  2.测试正则表达式是否匹配整个字符串 ====

<code python>
regex=ur"...\Z" #正则表达式末尾以\Z结束
if re.match(regex, subject):
    do_something()
else:
    do_anotherthing()
</code>


==== 3. 创建一个匹配对象，然后通过该对象获得匹配细节 ====

<code python>
regex=ur"..." #正则表达式
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()
</code>

==== 4.获取正则表达式所匹配的子串 ====
(Get the part of a string matched by the regex)
<code python>
regex=ur"..." #正则表达式
match = re.search(regex, subject)
if match:
    result = match.group()
else:
    result = ""
</code>

==== 5. 获取捕获组所匹配的子串 ====
(Get the part of a string matched by a capturing group)
<code python>
regex=ur"..." #正则表达式
match = re.search(regex, subject)
if match:
    result = match.group(1)
else:
    result = ""
</code>

==== 6. 获取有名组所匹配的子串 ====
(Get the part of a string matched by a named group)
<code python>
regex=ur"..." #正则表达式
match = re.search(regex, subject)
if match:
    result = match.group("groupname")
else:
    result = ""
</code>

==== 7. 将字符串中所有匹配的子串放入数组中 ====
(Get an array of all regex matches in a string)
<code python>
result = re.findall(regex, subject)
</code>

==== 8.遍历所有匹配的子串 ====
(Iterate over all matches in a string)
<code python>
for match in re.finditer(r"<(.*?)\s*.*?/\1>", subject)
    # match start: match.start()
    # match end (exclusive): match.end()
    # matched text: match.group()
</code>

==== 9.通过正则表达式字符串创建一个正则表达式对象 ====
(Create an object to use the same regex for many operations)
<code python>
reobj = re.compile(regex)
</code>

==== 10.用法１的正则表达式对象版本 ====
（use regex object for if/else branch whether (part of) a string can be matched）
<code python>
reobj = re.compile(regex)
if reobj.search(subject):
    do_something()
else:
    do_anotherthing()
</code>

==== 11.用法２的正则表达式对象版本 ====
（use regex object for if/else branch whether a string can be matched entirely）
<code python>
reobj = re.compile(r"\Z")　＃正则表达式末尾以\Z 结束
if reobj.match(subject):
    do_something()
else:
    do_anotherthing()
</code>


====  12.创建一个正则表达式对象，然后通过该对象获得匹配细节 ====
（Create an object with details about how the regex object matches (part of) a string）
<code python>
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()
</code>

==== 13.用正则表达式对象获取匹配子串 ====
（Use regex object to get the part of a string matched by the regex）
<code python>
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
    result = match.group()
else:
    result = ""
</code>

====  14.用正则表达式对象获取捕获组所匹配的子串 ====
（Use regex object to get the part of a string matched by a capturing group）
<code python>
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
    result = match.group(1)
else:
    result = ""
</code>

====  15.用正则表达式对象获取有名组所匹配的子串 ====
（Use regex object to get the part of a string matched by a named group）
<code python>
reobj = re.compile(regex)
match = reobj.search(subject)
if match:
    result = match.group("groupname")
else:
    result = ""
</code>

==== 16.用正则表达式对象获取所有匹配子串并放入数组 ====
（Use regex object to get an array of all regex matches in a string）
<code python>
reobj = re.compile(regex)
result = reobj.findall(subject)
</code>

==== 17.通过正则表达式对象遍历所有匹配子串 ====
（Use regex object to iterate over all matches in a string）
<code python>
reobj = re.compile(regex)
for match in reobj.finditer(subject):
    # match start: match.start()
    # match end (exclusive): match.end()
    # matched text: match.group()
</code>