Notes on Python regular expressions

Article Directory

• 0, Preface
• 1, Regular expression pattern
• 2. Regular expression modifier - optional flag
• • 2.1, `re.IGNORECASE`(`re.I`)
  • 2.2, `re.ASCII` (`re.A`)
  • 2.3, `re.DOTALL` (`re.S`)
  • 2.4, `re.MULTILINE`(`re.M`)
  • 2.5, `re.VERBOSE`(re.X)
  • 2.6, Superposition of modifiers
• 3, Regular expression function
• • 3.1. Function to find a single match
  • • Example 3.1.1
    • Example 3.1.2
    • Example 3.1. 3
  • 3.2. Function to find multiple matches
  • • Example 3.2.1
  • 3.3. Split
  • • Example 3.3.1
##

import re

0、Foreword

1. Regular expression pattern

2. Regular expression modifier - optional flag

2.1.re.IGNORECASE(re.I)

re.findallfunction because it is the function throughout this section.
re.findall(pattern, string, flag=0): Search from any position in the string and return a list.patternis the character (string) to be matched,stringis the search source,flagis the modifier, the default is 0

The function of re.Iis to ignore the case of characters

text = "I'm Jasmine-Feng. My student number is No. 321432"pattern = r"Jasmine-FENG"print('Default: ', re.findall(pattern,text))print('Ignore upper/lower case: ', re.findall(pattern,text,flags=re.I))

N.B.The pattern is assigned ar string. The function of this r string is to avoid Escape, r is the abbreviation of raw, which means keeping it as is. See this blog post. Generally speaking, this r string will be used when using regular expressions.

Default: []Ignore upper/lower case: ['Jasmine-Feng']Process finished with exit code 0

2.2. The function ofre.ASCII(re.A)

is Only matches characters supported by ASCII code, so which characters specifically do you mean? The picture below is from Baidu Encyclopedia.
Chinese characters are not included in this, so if the modifier isre.A
, then the Chinese characters cannot be matched~

text = "我是Jasmine-Feng. 我的学号是No. 321432"pattern = r"\w+"print('Default: ', re.findall(pattern,text))print('ASCII: ', re.findall(pattern,text,flags=re.A))

is used to match one or more alphanumeric and underlined Chinese characters

Default: ['我是Jasmine', 'Feng', '我的学号是No', '321432']ASCII: ['Jasmine', 'Feng', 'No', '321432']Process finished with exit code 0

re.DOTALL（re.S）In the regular expression pattern,

is used

text = "我\t是Jasmine-F\neng. 我%的◉学号是No. 321432"pattern = r'.*'print('Default: ', re.findall(pattern,text))print('DOTALL: ', re.findall(pattern,text,re.S))

is used to match characters with a length of at least 0 (String), emmm, it seems like nonsense? In fact, as long as the entire paragraph is not truncated by a newline character, you can get the entire string (plus an empty string).

Default: ['我\t是Jasmine-F', '', 'eng. 我%的◉学号是No. 321432', '']DOTALL: ['我\t是Jasmine-F\neng. 我%的◉学号是No. 321432', '']Process finished with exit code 0

re.MULTILINE(re.M)

Matching positioning To the end of the string,^locates the beginning of the string. By default, if you wrap a new line, you cannot locate the beginning/end of the new line. However, modifying it withre.Mwill Yes, that is multi-line mode.

text = "我\t是Jasmine-F\neng. 我%的◉\n学号是No. 321432"pattern = r'.$'pattern2 = r'^.'print('Default, end: ', re.findall(pattern, text))print('MULTILINE, end: ', re.findall(pattern, text, re.M))print('Default, start: ', re.findall(pattern2, text))print('MULTILINE, start: ', re.findall(pattern2, text, re.M))

Default, end: ['2']MULTILINE, end: ['F', '◉', '2']Default, start: ['我']MULTILINE, start: ['我', 'e', '学']Process finished with exit code 0

re.VERBOSE(re.X)verbose means "detailed and lengthy", through this modifier Comments can be added to

. Note that you are adding it topattern, not totext! At first I thought I could add comments totext, but I couldn’t get the result after debugging for a long time. . .

text = '朋友们好啊！我是xxxxxx拳掌门人xxx~'pattern = r'''朋友们 # 主语 好啊！ # 谓语 '''print(re.findall(pattern, text,re.VERBOSE))

['朋友们好啊！']Process finished with exit code 0

Use

to superimpose modifications.

text = 'Hello everybody!\n我是xxxxxx拳掌门人xxx~'pattern = r'BODY.*$'print(re.findall(pattern, text, re.I))print(re.findall(pattern, text, re.M))print(re.findall(pattern, text, re.M | re.I))

[][]['body!']Process finished with exit code 0

The above is the detailed content of Notes on Python regular expressions. For more information, please follow other related articles on the PHP Chinese website!