Recently opened a small library in git...
learning regular expression in python.
What are regular expressions?
Regular expressions are a method used to retrieve text that matches certain patterns from text.
Regular expressions match a string from left to right. The word "Regular Expression" is too long, we usually use its abbreviation "regex" or "regexp".
Regular expressions can be used to replace text in strings, validate forms, extract strings from a string based on pattern matching, and more.
What is this library for?
Many previous regular tutorials have tutorials that are out of language dependencies and use related languages for teaching.
But there are more or less some problems, for example, some grammars in regular tutorials that are completely out of language may not be consistent with the expected results when used in some languages.
So there is a display of some common regular usages implemented by this python, which is convenient for learning.
library content
Reprint please indicate the source~~
#!/usr/bin/python
import re
def main():
# <editor-fold desc='匹配任意字符关键字'>
pattern = re.compile(r'.a.\.xls')
result1 = pattern.findall('sales.xls'
'sales1.xls'
'orders3.xls'
'sales2.xls'
'sales3.xls'
'apac1.xls'
'europe2.xls'
'na1.xls'
'na2.xls'
'sa2.xls'
'ca1.xls')
print(result1) # ['na1.xls', 'na2.xls', 'sa2.xls', 'ca1.xls']
# </editor-fold>
# <editor-fold desc='匹配一组字符关键字[]'>
pattern = re.compile(r'[ns]a.\.xls')
result1 = pattern.findall('sales.xls'
'sales1.xls'
'orders3.xls'
'sales2.xls'
'sales3.xls'
'apac1.xls'
'europe2.xls'
'na1.xls'
'na2.xls'
'sa2.xls'
'ca1.xls')
print(result1) # ['na1.xls', 'na2.xls', 'sa2.xls']
# </editor-fold>
# <editor-fold desc='大小写'>
pattern = re.compile(r'[Rr]eg[Ee]x')
result1 = pattern.findall('RegEx or regex or REGEX.')
print(result1) # ['RegEx', 'regex']
# </editor-fold>
# <editor-fold desc='集合区间'>
pattern = re.compile(r'[ns]a[0123456789]\.xls')
pattern = re.compile(r'[ns]a[0-9]\.xls')
result1 = pattern.findall('sales.xls'
'sales1.xls'
'orders3.xls'
'sales2.xls'
'sales3.xls'
'apac1.xls'
'europe2.xls'
'sam.xls'
'na1.xls'
'na2.xls'
'sa1.xls'
'ca1.xls')
print(result1) # ['na1.xls', 'na2.xls', 'sa1.xls']
# </editor-fold>
# <editor-fold desc='读取rgb值'>
# [A-Z] 匹配A到Z所有大写字母
# [a-z] 匹配a到z所有小写字母
# [A-F] 匹配A到F所有大写字母
# [A-z] 匹配从ASCII字符A到ASCII字符z的所有字母
# [A-Za-z0-9] 匹配任何一个字母无论大小写或数字
pattern = re.compile(r'#[0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f]')
result1 = pattern.findall('body { background-color: #fefdb8; }'
'h1 { background-color: #0000ff; }'
'div { background-color: #d0f4e6; }'
'span { background-color: #f08970; }')
print(result1) # ['#fefdb8', '#0000ff', '#d0f4e6', '#f08970']
# </editor-fold>
# <editor-fold desc='排除关键字^'>
pattern = re.compile(r'[ns]a[^0-9]\.xls')
result1 = pattern.findall('sales.xls'
'sales1.xls'
'orders3.xls'
'sales2.xls'
'sales3.xls'
'apac1.xls'
'europe2.xls'
'sam.xls'
'na1.xls'
'na2.xls'
'sa1.xls'
'ca1.xls')
print(result1) # ['sam.xls']
# </editor-fold>
# <editor-fold desc='匹配空白字符'>
# 关键字
# [\b] 回退(并删除)一个字符(Backspace)
# \f 换页符
# \n 换行符
# \r 回车符
# \t 制表符
# \v 垂直制表符
pattern = re.compile(r'\r\n\r\n')
result1 = pattern.findall('101'
'202'
""
'303')
print(result1) # 匹配空行
# </editor-fold>
# <editor-fold desc='匹配特定字符串类型'>
# 匹配数字,非数字
# \d 任何一个数字字符 等价 [0-9]
# \D 任何一个非数字字符 等价 [^0-9]
# 匹配字母数字,非字母数字
# \w 任何一个字母数字字符(大小写均可)或下划线字符(等价于[a-zA-Z0-9_])
# \W 任何一个非字母数字字符或非下划线字符(等价于[^a-zA-Z0-9_])
pattern = re.compile(r'\w\d\w\d\w\d')
result1 = pattern.findall('11213\r\n'
'A1C2E3\r\n'
'48075\r\n'
'48237\r\n'
'M1B4F2\r\n'
'90046\r\n'
'H1H2H2\r\n')
print(result1) # ['A1C2E3', 'M1B4F2', 'H1H2H2']
# </editor-fold>
# <editor-fold desc='匹配空白字符,非空白字符'>
# \s 任何一个空白字符 等价 [\f\n\r\t\v]
# \S 任何一个非空白字符 等价 [^\f\n\r\t\v]
# </editor-fold>
# <editor-fold desc='匹配十六进制或八进制数值'>
# \x 十六进制
# ex: \x0A 对应ASCII10 等价于 \n
# \0 八进制
# ex: \011 对应ASCII9 等价于\t
# </editor-fold>
# <editor-fold desc='POSIX, 不过py不支持'>
# [:alnum:] 任何一个字母或数字(等价于[a-zA-Z0-9])
# [:alpha:] 任何一个字母(等价于[a-zA-Z])
# [:blank:] 空格或制表符(等价于[\t ])
# [:cntrl:] ASCII控制字符(ASCII 0到31, 再加上ASCII 127)
# [:digit:] 任何一个数字(等价于[0-9])
# [:graph:] 和[:print:]一样,但不包括空格
# [:lower:] 任何一个小写字母(等价于[a-z])
# [:print:] 任何一个可打印字符
# [:punct:] 既不属于[:alnum:], 也不属于[:cntrl:]的任何一个字符
# [:space:] 任何一个空白字符,包括空格(等价于[\f\n\r\t\v\ ])
# [:upper:] 任何一个大写字母(等价于[A-Z])
# [:xdigit:] 任何一个十六进制数字(等价于[a-fA-F0-9])
# </editor-fold>
# <editor-fold desc='匹配一个或多个字符'>
# +号匹配 1~N个字符
# []内\.和.等价
pattern = re.compile(r'[\w\.]+@[\w.]+\.\w+')
result1 = pattern.findall('[email protected]\n'
'[email protected]\n'
'[email protected]\n'
'[email protected]\n'
'[email protected]\n')
# ['[email protected]', '[email protected]', '[email protected]', '[email protected]', '[email protected]']
print(result1)
# </editor-fold>
# <editor-fold desc='匹配零个或多个字符'>
# *号匹配 0~N个字符
# []内\.和.等价
pattern = re.compile(r'\w+[\w.]*@[\w.]+\.\w+')
result1 = pattern.findall('[email protected]\n'
'[email protected]\n')
# ['[email protected]', '[email protected]']
print(result1)
# </editor-fold>
# <editor-fold desc='匹配零个或一个字符'>
# ?号匹配 0~1个字符(最多一次)
pattern = re.compile(r'https?:\/\/[\w.\/]+')
result1 = pattern.findall('http://www.forta.com/ test https://www.forta.com/')
# ['http://www.forta.com/', 'https://www.forta.com/']
print(result1)
# </editor-fold>
# <editor-fold desc='匹配重复次数'>
# {次数}
pattern = re.compile(r'#[0-9A-Fa-f]{6}')
result1 = pattern.findall('body { background-color: #fefdb8; }'
'h1 { background-color: #0000ff; }'
'div { background-color: #d0f4e6; }'
'span { background-color: #f08970; }')
print(result1) # ['#fefdb8', '#0000ff', '#d0f4e6', '#f08970']
# </editor-fold>
# <editor-fold desc='区间范围'>
# {最小, 最大} ex:{2, 4} 最少重复2次, 最多重复4次
# {0,1} 等价于 ?
pattern = re.compile(r'\d{1,2}[-\/]\d{1,2}[-\/]\d{2,4}')
result1 = pattern.findall('4/8/17\n'
'10-6-2018\n'
'2/2/2\n'
'01-01-01\n')
# ['4/8/17', '10-6-2018', '01-01-01']
print(result1)
# </editor-fold>
# <editor-fold desc='至少重复多少次'>
# {至少次数,} 重复 至少次数 或更多
# {1,} 等价于 +
# 找出金额大于100的
pattern = re.compile(r'\d+: \$\d{3,}\.\d{2}')
result1 = pattern.findall('1001: $496.80\n'
'1002: $1290.69\n'
'1003: $26.43\n'
'1004: $613.42\n'
'1005: $7.61\n'
'1006: $414.90\n'
'1007: $25.00\n')
# ['1001: $496.80', '1002: $1290.69', '1004: $613.42', '1006: $414.90']
print(result1)
# </editor-fold>
# <editor-fold desc='防止过度匹配'>
# * + {} 都是greedy型
# 后面添加?就是 懒惰版本
# ['<b>AK</b> and <b>HI</b>']
pattern = re.compile(r'<[Bb]>.*<\/[Bb]>')
# ['<b>AK</b>', '<b>HI</b>']
pattern = re.compile(r'<[Bb]>.*?<\/[Bb]>')
result1 = pattern.findall('This offer is not available to customer living in <b>AK</b> and <b>HI</b>')
print(result1)
# </editor-fold>
# <editor-fold desc='单词边界'>
# \b 匹配单词边界
pattern = re.compile(r'\bcat\b')
result1 = pattern.findall('The cat scattered his food all over the room.')
# ['cat']
print(result1)
pattern = re.compile(r'\bcap')
result1 = pattern.findall('captain cap cape recap')
# ['cap', 'cap', 'cap']
print(result1)
pattern = re.compile(r'cap\b')
result1 = pattern.findall('captain cap cape recap')
# ['cap', 'cap']
print(result1)
# </editor-fold>
# <editor-fold desc='非单词边界'>
# \B 匹配非单词边界
pattern = re.compile(r'\B-\B')
result1 = pattern.findall('color - coded nine-digit')
# ['-']
print(result1)
# </editor-fold>
# <editor-fold desc='字符串边界'>
# ^ 字符串开头 ([]内^才是取反)
# $ 字符串结尾
# 如果xml之前有其他字符或者其他行, 就会匹配失败
# ['<?xml version='1.0' encoding='utf-8'?>']
pattern = re.compile(r'^\s*<\?xml.*\?>')
# 匹配尾巴的
# ['<manifest>']
pattern = re.compile(r'<manifest>$')
result1 = pattern.findall('<?xml version=\'1.0\' encoding=\'utf-8\'?><manifest><manifest>')
print(result1)
# </editor-fold>
# <editor-fold desc='多行模式'>
# (?m) 打开多行模式, 打开后会把换行符视为字符串分隔符
# 这样就可以用^$匹配字符串换行后的起始和结束位置
pattern = re.compile(r'(?m)^\s*\/\/.*$')
result1 = pattern.findall('// 注释1 \n'
'code123\n'
'// 注释2\n'
'code123 \n'
'//注释123 注释456')
# ['// 注释1 ', '// 注释2', '//注释123 注释456']
print(result1)
# </editor-fold>
# <editor-fold desc='子表达式'>
# () 关键字
# 无法正确匹配, 只能匹配 ;;
pattern = re.compile(r' {2,}')
pattern = re.compile(r'( ){2,}')
result1 = pattern.findall('Test Test')
# ['// 注释1 ', '// 注释2', '//注释123 注释456']
print(result1)
# ['12.123.12.200']
pattern = re.compile(r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}')
# [('12.123.14.200', '14.')]
pattern = re.compile(r'((\d{1,3}\.){3}\d{1,3})')
# ['14.']
pattern = re.compile(r'(\d{1,3}\.){3}\d{1,3}')
# ['12.123.14.200']
pattern = re.compile(r'(?:\d{1,3}\.){3}\d{1,3}')
result1 = pattern.findall('[12.123.14.200]')
print(result1)
# <re.Match object; span=(1, 14), match='12.123.14.200'>
print(re.search(pattern, '[12.123.14.200]'))
# [('1967', '19')]
pattern = re.compile(r'((19|20)\d{2})')
result1 = pattern.findall('1967-08-17')
print(result1)
# </editor-fold>
# <editor-fold desc='补充上面子表达式中的()和findall在py下的注意'>
s = 'adfad asdfasdf asdfas asdfawef asd adsfas '
reObj1 = re.compile(r'((\w+)\s+\w+)')
# [('adfad asdfasdf', 'adfad'), ('asdfas asdfawef', 'asdfas'), ('asd adsfas', 'asd')]
print(reObj1.findall(s))
reObj2 = re.compile(r'(\w+)\s+\w+')
# ['adfad', 'asdfas', 'asd']
print(reObj2.findall(s))
reObj3 = re.compile(r'\w+\s+\w+')
# ['adfad asdfasdf', 'asdfas asdfawef', 'asd adsfas']
print(reObj3.findall(s))
# 按以上代码例子讲解:
#
# findall函数返回的总是正则表达式在字符串中所有匹配结果的列表
# 此处主要讨论列表中'结果'的展现方式
# 即findall中返回列表中每个元素包含的信息
# 1.当给出的正则表达式中带有多个括号时
# 列表的元素为多个字符串组成的tuple
# tuple中字符串个数与括号对数相同
# 字符串内容与每个括号内的正则表达式相对应
# 并且排放顺序是按括号出现的顺序。
#
# 2.当给出的正则表达式中带有一个括号时
# 列表的元素为字符串
# 此字符串的内容与括号中的正则表达式相对应(不是整个正则表达式的匹配内容)
#
# 3.当给出的正则表达式中不带括号时
# 列表的元素为字符串
# 此字符串为整个正则表达式匹配的内容
#
# </editor-fold>
# <editor-fold desc='匹配有效ip'>
# 注意顺序
pattern = re.compile(
r'((((25[0-5])|(2[0-4]\d)|(1[0-9]\d)|(\d{1,2}))\.){3}((25[0-5])|(2[0-4]\d)|(1[0-9]\d)|(\d{1,2})))')
result1 = pattern.findall('[12.159.46.200]')
# [('12.159.46.200', '46.', '46', '', '', '159', '46', '200', '', '200', '', '')]
print(result1)
# 替换成更符合逻辑的写法会有问题
# 从左往右匹配, 如果满足就会给出结果
pattern = re.compile(
r'((((\d{1,2})|(1[0-9]\d)|(2[0-4]\d)|(25[0-5])|)\.){3}((\d{1,2})|(1[0-9]\d)|(2[0-4]\d)|(25[0-5])|))')
result1 = pattern.findall('[12.159.46.200]')
# [('12.159.46.20', '46.', '46', '46', '159', '', '', '20', '20', '', '', '')]
print(result1)
# </editor-fold>
# <editor-fold desc='反向引用或回溯引用(backreference)'>
# ()代表一个子表达式
# 之后使用\n(1开始)代表引用先前的第n个表达式
# 部分正则实现中\0可以代表整个表达式
# 注意多个()的情况
# ['of', 'and', 'are']
pattern = re.compile(r'[ ](\w+)[ ]\1')
# [(' of ', 'of'), (' and ', 'and'), (' are ', 'are')]
pattern = re.compile(r'([ ](\w+)[ ])\2')
# [(' of of', 'of'), (' and and', 'and'), (' are are', 'are')]
pattern = re.compile(r'([ ](\w+)[ ]\2)')
result1 = pattern.findall('xx of of xxx and and xxx are are.')
print(result1)
pattern = re.compile(r'(<[hH]([1-6])>.*?<\/[hH]\2>)')
result1 = pattern.findall('<body>\n'
'<h1>Test1</h1>\n'
'Test2\n'
'<h2>Test3</h2>\n'
'Test4\n'
'<h3>Test5</h3>\n'
'Test6<br/>\n'
'</body>\n')
# [('<h1>Test1</h1>', '1'), ('<h2>Test3</h2>', '2'), ('<h3>Test5</h3>', '3')]
print(result1)
# </editor-fold>
# <editor-fold desc='替换操作'>
# 替换的串中和backreference一样使用\n替换子表达式
pattern = re.compile(r'([\w\.]+@[\w.]+\.\w+)')
s = '[email protected]\n' + \
'abcdefg\n' + \
'[email protected]\n' + \
'abcdefg'
result1 = pattern.findall(s)
replstr = r'<a href="mailto:\1">\1</a>'
# ['[email protected]', '[email protected]']
print(result1)
print('---------------')
print(s)
print('----↓↓↓↓↓↓↓----')
print(pattern.sub(replstr, s))
print('---------------')
pattern = re.compile(r'(\d{3})(-)(\d{3})(-)(\d{4})')
s = '333-157-1507\n' + \
'123-403-1570\n' + \
'111-578-8456\n' + \
'234-237-4856'
result1 = pattern.findall(s)
replstr = r'(\1) \3-\5'
# [('333', '-', '157', '-', '1507'),
# ('123', '-', '403', '-', '1570'),
# ('111', '-', '578', '-', '8456'),
# ('234', '-', '237', '-', '4856')]
print(result1)
print('---------------')
print(s)
print('----↓↓↓↓↓↓↓----')
print(pattern.sub(replstr, s))
print('---------------')
# </editor-fold>
# <editor-fold desc='大小写转换'>
# 正则配合backreference
# \E \L,\U的结束符
# \l 将下一个字符转换成小写
# \L 将\L至\E之间的字符都转换成小写
# \u 将下一个字符转换成大写
# \U 将\U至\E之间的字符都转换成小写
# py的话需要像下面这样处理
# 以上关键字会报错
pattern = re.compile(r'([\w\.]+@[\w.]+\.\w+)')
s = '[email protected]\n' + \
'abcdefg\n' + \
'[email protected]\n' + \
'abcdefg'
result1 = pattern.findall(s)
# 'Test[{\U\1\E}]
def callback(word): return 'Test[{}]'.format(word.group(1).upper())
# ['[email protected]', '[email protected]']
print(result1)
print('---------------')
print(s)
print('----↓↓↓↓↓↓↓----')
print(pattern.sub(callback, s))
print('---------------')
# </editor-fold>
# <editor-fold desc='向前查找'>
# 查看已匹配文本之后的内容
# (?=)
# ['https:', 'https:']
pattern = re.compile(r'.+:')
# ['https', 'https']
pattern = re.compile(r'.+(?=:)')
result1 = pattern.findall('https://www.bilibili.com/\n'
'https://www.baidu.com/\n')
print(result1)
# </editor-fold>
# <editor-fold desc='向后查找'>
# (?<=)
pattern = re.compile(r'(?<=\$)[\d.]+')
result1 = pattern.findall('1.24\n'
'4685.6845\n'
'$ 4685.6845\n'
'$15978685.45\n'
'$12346785852.54$\n'
'4568.96 $64987.69\n')
# ['15978685.45', '12346785852.54', '64987.69']
print(result1)
# </editor-fold>
# <editor-fold desc='结合向前向后'>
pattern = re.compile(r'(?<=\<[tT][iI][tT][lL][eE]\>).*(?=\<\/[tT][iI][tT][lL][eE]\>)')
result1 = pattern.findall('<head>\n'
'<title>Test 123 learning regex.</title>\n'
'</head>')
# ['Test 123 learning regex.']
print(result1)
# </editor-fold>
# <editor-fold desc='否定式环视'>
# = 替换为 !
# ?= --> ?!
# ?<= --> ?<!
pattern = re.compile(r'\b(?<!\$)\d+\b')
result1 = pattern.findall('1 24\n'
'$30\n'
'200\n'
'$ 300123\n'
'$15945\n'
'$123454$\n'
'456896 $6498769\n')
# ['1', '24', '466845', '4686845', '456896']
print(result1)
# </editor-fold>
# <editor-fold desc='子表达式条件'>
# ?(n) n为子条件序号
# 添加条件判断
# 下面这个的解释:
# 直观的看可能比较懵逼
# 第一步先搜索左括号(
# 如果有左括号才匹配后面出现的右括号
# 否则就匹配-
# [('123-456-7890', ''), ('(123)456-7890', '('), ('123-456-7890', '')]
pattern = re.compile(r'((\()?\d{3}(?(2)\)|-)\d{3}-\d{4})')
# [('123-456-7890', '', '-', ''), ('(123)456-7890', '(', ')', ''), ('(123-456-7890', '(', '-', '')]
pattern = re.compile(r'((\()?\d{3}((2)?\)|-)\d{3}-\d{4})')
result1 = pattern.findall('123-456-7890\n'
'(123)456-7890\n'
'(123)-456-7890\n'
'(123-456-7890\n'
'1234567890\n'
'123 456 7890\n')
# [('123-456-7890', ''), ('(123)456-7890', '('), ('123-456-7890', '')]
print(result1)
# 配合?=使用
pattern = re.compile(r'(\d{5}((?=-)?-\d{4}))')
result1 = pattern.findall('11111\n'
'22222\n'
'33333-\n'
'44444-5555\n')
# [('44444-5555', '-5555')]
print(result1)
# </editor-fold>
if __name__ == '__main__':
main()
pass