import re
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1 Find the first matching string

s = 'i love python very much'
pat = 'python' 
r = re.search(pat,s)
print(r.span()) #(7.13)
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2 finds all 1’s

s = Class 1, Senior 3, Qingzhou No.1 Middle School, Weifang City, Shandong Province
pat = '1'
r = re.finditer(pat,s)
for i in r:
    print(i)

# <re.Match object; span=(9.10), match='1'>
# <re.Match object; span=(14.15), match='1'>
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3 \d Match digit [0-9]

s = 'total 20 lines of code running time 13.59s'
pat = r'\d+'# + denotes a matching number (\d denotes a generic character for a number)1R = re.findall(pat,s)print(r)
# ['20'.'13'.'59']
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We want to keep 13.59 rather than separate, see 4

4? Indicates that the preceding character matches 0 or 1 times

s = 'total 20 lines of code running time 13.59s'
pat = r'\d+\.? \d+'#? Match decimal point (\.)0Time or1R = re. Once the.findall (pat, s)print(r)
# ['20'.'13.59']
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5 ^ matches the beginning of the string

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'^[emrt]'R = re.findall(pat,s)print(r) # [], because the string begins with a character`T`, is not in the emRT matching range, so return nullCopy the code

6 Re. I ignores case

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'^[emrt]'R = re.compile(pat, re.i).search(s)print(r)
# <re.Match object; span=(0.1), match='T'> indicates that the beginning of the string is in the match listCopy the code

This is an inaccurate version, see # 9

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'\s[a-zA-Z]+'  
r = re.findall(pat,s)
print(r) #[' module'.' provides'.' regular'.' expression'.' matching'.' operations'.' similar'.' to'.' those'.' found'.' in'.' Perl']
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8 only capture words, remove Spaces and use () capture, this is inaccurate version, see # 9

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'\s([a-zA-Z]+)'  
r = re.findall(pat,s)
print(r) #['module'.'provides'.'regular'.'expression'.'matching'.'operations'.'similar'.'to'.'those'.'found'.'in'.'Perl']
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9 add the 8th above the first word, see the extracted word does not include the first word, use? Indicates 0 or 1 occurrences of the preceding character, but this character also indicates greedy or non-greedy matching. Use caution.

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'\s? ([a-zA-Z]+)'  
r = re.findall(pat,s)
print(r) #['This'.'module'.'provides'.'regular'.'expression'.'matching'.'operations'.'similar'.'to'.'those'.'found'.'in'.'Perl']
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Use the above method to split words, not concise, just for demonstration. The easiest way to split a word is to use the split function.

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'\s+'  
r = re.split(pat,s)
print(r) # ['This'.'module'.'provides'.'regular'.'expression'.'matching'.'operations'.'similar'.'to'.'those'.'found'.'in'.'Perl']
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11 Extract words beginning with m or T, ignore case the result below is not what we want, the reason is? On!

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'\s? ([mt][a-zA-Z]*)'R = re.findall(pat,s)print(r) # ['module'.'matching'.'tions'.'milar'.'to'.'those']
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12 Use ^ to find the word at the beginning of the string. Combine 11 and 12 to get all words beginning with m or t

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'^([mt][a-zA-Z]*)\s'R = re.compile(pat, re.i).findall(s)print(r) # ['This']
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13 Split the words first and then search for the words that meet the requirements. Use match to indicate whether the words match

s = 'This module provides regular expression matching operations similar to those found in Perl'
pat = r'\s+'  
r = re.split(pat,s)
res = [i for i in r if re.match(r'[mMtT]',i)] 
print(res) # ['This'.'module'.'matching'.'to'.'those']
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14 Greedy to match as many matching characters as possible

content='<h>ddedadsad</h><div>graph</div>bb<div>math</div>cc'
pat=re.compile(r"<div>(.*)</div>"M =pat.findall(content)print(m) # ['graph</div>bb<div>math']
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15 non-greedy match has only one more question mark (?) than 14. And get completely different results.

content='<h>ddedadsad</h><div>graph</div>bb<div>math</div>cc'
pat=re.compile(r"
      

       (.*?) 
      
"M =pat.findall(content)print(m) # ['graph'.'math']
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The difference between greedy matching and non-greedy matching is that the latter is returned immediately after the string is matched.

16 contains a variety of separators using the split function

content = 'graph math,,english; chemistry'# this pat=re.com running (r"[\s\,\;] +"M =pat.split(content)print(m) # ['graph'.'math'.'english'.'chemistry']
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The sub function implements the substitution of matched substrings

content="hello 12345, hello 456321"    
pat=re.compile(r'\d+'M =pat.sub()"666",content)
print(m) # hello Awesome!, hello Awesome!
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18 climb baidu home page title

import re
from urllib importData =request.urlopen("http://www.baidu.com/").read().decode() # parse the web page and determine the regular expression pat=r'(.*?) '

result=re.search(pat,data)
print(result) <re.Match object; span=(1358.1382), match= "> < span style =" max-width: 100%; clear: bothCopy the code

19 Summary of common metacharacters

. Matches any character ^ matches at the beginning of the string $Matches at the end of the string * before the atom repeats0time1Many times? Repeat the preceding atom once or0Times + the preceding atom repeats once or more {n} the preceding atom occurs n times {n,} the preceding atom occurs at least n times {n,m} the preceding atom occurs between n-m () grouping, the part that needs to be outputCopy the code

20 Summary of common characters

\s matches blank characters \w matches any letters/digits/underscores \w and lowercase w conversely, matches any characters other than letters/digits/underscores \d matches decimal digits \d matches values other than decimal numbers [09 -[match a09 -The digits between [A-z] match lowercase letters. [A-z] match uppercase lettersCopy the code

This is a summary of the basic use of the regular module in Python, with a step-by-step optimization analysis process. This is an intermediate process, but it is essential to understand the regular module. The author also has a superficial understanding of regularity. If there is any inadequacy in the summary, please correct me.

Note: the menu of the official account includes an AI cheat sheet, which is very suitable for learning on the commute.

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