[编程经验] Python正则表达式
Hello，大家好。又见面了，今天给大家介绍一下，正则表达式在Python中是如何使用的。这样说的原因是正则表达式并不是Python所独有的，而是自成体系，在很多地方都有使用。而正则表达式在Python中主要是re模块来实现的，所以学习Python正则表达式主要就是学习re模块，然后需要熟悉正则表达式的语言，这样基本就可以掌握了。
# re模块
re模块中常用的函数有
compile， findall，match，search，sub，split
compile函数的作用是编译一个正则表达式模板，返回一个模板的对象（实例）。complie函数一般是配合findall来使用的，findall，的意思就是说有了一个模板的对象以后，用这个对象去匹配你想匹配的字符串，然后把匹配到的全部以列表形式返回。函数search也是用来在一个字符串中找模板对象所匹配到的字符，如果多次匹配成功只返回第一个。match函数只会匹配字符串的开头，如果匹配失败，则返回None。而sub函数的意思是替换的意思，split是分割，根据指定的字符分割字符串，而Python字符串分割的主要区别是可以选择多个分割符，而Python字符串自带的分割方法只能选择一个分割符。下面写个简单的栗子，这里不用管为啥去匹配那个，只是个栗子，让大家看看正则表达式的语法是怎么样的。
这篇文章写得比较简单，之所以这样是因为不想让大家觉得正则表达式这块的内容很多，其实没有想象的那么难，基本就这些东西，学会这个也就够用了。文章没有排版，主要作者太懒，看着不爽的话，可以看下后面的一个参考链接。
# - * - coding:utf-8 - * -
import re
# complie, findall, search, match, sub, split
test_string = 'abc|2abcd)3Hello world4abcddd,\n 2017-11-19|Python正则表达式详解'
patterns = [
"Hello world", # 匹配Hello world
"\d+", # 匹配所有数字，\d表示匹配数字，+号表示匹配前1个字符1次或者无限次
"abcd?", # 匹配abc和abcd，？号表示匹配前一个字符0次或者1次
"abcd*", # 星号*匹配前一个字符0次或者无数次
"\w", # 小写w匹配单词字符
"\W", # 匹配非单词字符
"\d+\-\d+\-\d+", # 匹配以横线分割的日期
"^a[bc]d?", # ^表示匹配字符串的开头
"\|.", # \表示转义字符，.表示匹配除换行符以外的字符
"\d", # 匹配数字
"\d+|\w+", # |表示匹配左右2个表达式任意一个
"\s", # 匹配空白字符
"\s\w+", # 匹配空白字符后跟着的单词字符
".", # 匹配除换行符以外的字符
"\D", # 匹配非数字字符
"\S", # 大写S匹配任意非空字符
]
for pattern in patterns:
print "- "*20
print("current regex is : {}".format(pattern))
p = re.compile(pattern).findall(test_string)
if p:
print("findall results is: {}".format(p))
else:
print("[!] match failed ")
p1 = re.search(pattern, test_string, flags=0)
if p1:
result = p1.group()
print("search results is :{}".format(result))
else:
print("[!] match failed ")
p2 = re.match(pattern, test_string, flags=0)
if p2:
result = p1.group()
print("match results is :{}".format(result))
else:
print("[!] match failed ")
print("- "*20)
test_string = '2017,11,19'
re_sub = re.sub(",", ":", test_string)
print(re_sub)
print("- "*20)
test_string = "2017,11,19"
re_split = re.split(",", test_string)
print(re_split)
"""正则表达式就说到这里，入门以后主要还是要多练，然后结合具体的任务多尝试，如果能掌握好的，会省事很多
"""
- - - - - - - - - - - - - - - - - - - -
current regex is : Hello world
findall results is: ['Hello world']
search results is :Hello world
[!] match failed
- - - - - - - - - - - - - - - - - - - -
current regex is : \d+
findall results is: ['2', '3', '4', '2017', '11', '19']
search results is :2
[!] match failed
- - - - - - - - - - - - - - - - - - - -
current regex is : abcd?
findall results is: ['abc', 'abcd', 'abcd']
search results is :abc
match results is :abc
- - - - - - - - - - - - - - - - - - - -
current regex is : abcd*
findall results is: ['abc', 'abcd', 'abcddd']
search results is :abc
match results is :abc
- - - - - - - - - - - - - - - - - - - -
current regex is : \w
findall results is: ['a', 'b', 'c', '2', 'a', 'b', 'c', 'd', '3', 'H', 'e', 'l', 'l', 'o', 'w', 'o', 'r', 'l', 'd', '4', 'a', 'b', 'c', 'd', 'd', 'd', '2', '0', '1', '7', '1', '1', '1', '9', 'P', 'y', 't', 'h', 'o', 'n', '正', '则', '表', '达', '式', '详', '解']
search results is :a
match results is :a
- - - - - - - - - - - - - - - - - - - -
current regex is : \W
findall results is: ['|', ')', ' ', ',', '\n', ' ', '-', '-', '|']
search results is :|
[!] match failed
- - - - - - - - - - - - - - - - - - - -
current regex is : \d+\-\d+\-\d+
findall results is: ['2017-11-19']
search results is :2017-11-19
[!] match failed
- - - - - - - - - - - - - - - - - - - -
current regex is : ^a[bc]d?
findall results is: ['ab']
search results is :ab
match results is :ab
- - - - - - - - - - - - - - - - - - - -
current regex is : \|.
findall results is: ['|2', '|P']
search results is :|2
[!] match failed
- - - - - - - - - - - - - - - - - - - -
current regex is : \d
findall results is: ['2', '3', '4', '2', '0', '1', '7', '1', '1', '1', '9']
search results is :2
[!] match failed
- - - - - - - - - - - - - - - - - - - -
current regex is : \d+|\w+
findall results is: ['abc', '2', 'abcd', '3', 'Hello', 'world4abcddd', '2017', '11', '19', 'Python正则表达式详解']
search results is :abc
match results is :abc
- - - - - - - - - - - - - - - - - - - -
current regex is : \s
findall results is: [' ', '\n', ' ']
search results is :
[!] match failed
- - - - - - - - - - - - - - - - - - - -
current regex is : \s\w+
findall results is: [' world4abcddd', ' 2017']
search results is : world4abcddd
[!] match failed
- - - - - - - - - - - - - - - - - - - -
current regex is : .
findall results is: ['a', 'b', 'c', '|', '2', 'a', 'b', 'c', 'd', ')', '3', 'H', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd', '4', 'a', 'b', 'c', 'd', 'd', 'd', ',', ' ', '2', '0', '1', '7', '-', '1', '1', '-', '1', '9', '|', 'P', 'y', 't', 'h', 'o', 'n', '正', '则', '表', '达', '式', '详', '解']
search results is :a
match results is :a
- - - - - - - - - - - - - - - - - - - -
current regex is : \D
findall results is: ['a', 'b', 'c', '|', 'a', 'b', 'c', 'd', ')', 'H', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd', 'a', 'b', 'c', 'd', 'd', 'd', ',', '\n', ' ', '-', '-', '|', 'P', 'y', 't', 'h', 'o', 'n', '正', '则', '表', '达', '式', '详', '解']
search results is :a
match results is :a
- - - - - - - - - - - - - - - - - - - -
current regex is : \S
findall results is: ['a', 'b', 'c', '|', '2', 'a', 'b', 'c', 'd', ')', '3', 'H', 'e', 'l', 'l', 'o', 'w', 'o', 'r', 'l', 'd', '4', 'a', 'b', 'c', 'd', 'd', 'd', ',', '2', '0', '1', '7', '-', '1', '1', '-', '1', '9', '|', 'P', 'y', 't', 'h', 'o', 'n', '正', '则', '表', '达', '式', '详', '解']
search results is :a
match results is :a
- - - - - - - - - - - - - - - - - - - -
2017:11:19
- - - - - - - - - - - - - - - - - - - - ['2017', '11', '19']
参考：
http://www.cnblogs.com/huxi/archive/2010/07/04/1771073.html
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原始发表：2017-11-19，如有侵权请联系 cloudcommunity@tencent.com 删除
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