I. Functions
Function: the compile function is used to compile a regular expression and generate a regular expression (Pattern) object for use by the match() and search() functions.
Case: How to tell if it's a regular cell phone number
phone='''
weref234
16888888888
as13423423
weq
435435
15812312312e
afa15812312316
13111111111
'''
pattern=(r'1[3-9]\d{9}') #todo compiles a regular expression and then gets a compiled object
result=(phone) The #todo search will only return the first match, if no match is made it returns None.
print(result) #todo < object; span=(10, 21), match='15812312312'>Print results:
< object; span=(10, 21), match=‘16888888888’>
16888888888
(10, 21)
🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥 Special Note 1
result=(phone): search match successful return is the Match object; search will only return the first match results, if there is no successful match then return None
(): Returns the first match.
(): return the subscript of the first match, why is it (10, 21) na?
weref234: starting from 0, after the end of 4 also contains the newline character '/n' 2 characters, so starting from 10, does not contain 21, the principle of the front closed and then open
🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥 Special Note 2
match function: match match successful return is the Match object; role used to match the first note is the first character, where the first is in the string of characters being searched on the first index; if the first character does not match, return None
phone='''
weref234
16888888888
as13423423
weq
435435
15812312312e
afa15812312316
13111111111
'''
pattern=(r'1[3-9]\d{9}') #todo compiles a regular expression and then gets a compiled object
result2=(phone)
print(result2)Prints None, because the first character starts with a w, so it doesn't match the
phone1="17812312345aaa"
pattern=(r'1[3-9]\d{9}') #todo compiles a regular expression and then gets a compiled object
result2=(phone1) The #todo match function matches from the first character (starting with w) and returns None if the first character does not match.
print(result2)
print(()) #todo Returns the first match
print(()) #todo Returns the subscript of the first matching result
Print results:
< object; span=(0, 11), match=‘17812312345’>
17812312345
(0, 11)
II. Regular expressions
Expression character
. : matches any single character (excluding newlines)
[]: match the character set, the set in the interval, can match any one of the characters
\d: matches a number, i.e. 0-9, which can be expressed as [0-9],
\s: matches blank characters, i.e. spaces
\S: matches non-blank characters.
\w: matches word characters, i.e. a-z, A-Z, 0-9, _
\W: Match non-word characters
import re
#. Match any single character (excluding newlines)
one='123a'
res=('.',one)
print(())
#[]: match the set of characters, the set in the interval, can match any one of the characters
two='8'
res1=('[0-9]',two) #Match numbers between 1-9
print(())
res2=('[0,1,8,9]',two) #Match numbers between 0, 1, 8, 9
print(())
two_2='Hello Python'
print(('[hH]',two_2).group()) #Match lowercase or uppercase H
#\d: match numbers, i.e. 0-9, can be expressed as [0-9]
three='Sky 1 Launched Successfully'
print(('Sky\d',three).group())
print(('\d',three).group())
express a number
*: matches 0 or unlimited occurrences of the previous character, i.e., can be present or absent
+: matches 1 or an infinite number of occurrences of the previous character, i.e. at least 1 time
? : matches 1 or 0 occurrences of the previous character, i.e., either 1 or none.
{m}: matches m occurrences of the previous character
{m, }: match the previous character at least m times
{m, n}: matches the previous character appearing from m to n times
Requirement 1: Match a string where the first letter is uppercase and the subsequent letters must be lowercase or none at all
print(('[A-Z][a-z]*','Mn').group())
print(('[A-Z][a-z]*','Msdfsg').group())
print(('[A-Z][a-z][a-z]','Msdfs').group())
Mn
Msdfsg
Msd
Requirement 2 Match a variable name that
print((r'[a-zA-Z_]+[\w]*','name1').group()) print((r'[a-zA-Z_]+[\w]*','_name1').group()) print((r'[a-zA-Z_]+[\w]*','2_name1'))
name1
_name1
None
Requirement 3: Match any number between 0-99
print(('[0-9]?[0-9]','88').group())
print(('[0-9]?[0-9]','8').group())
print(('[0-9]?[0-9]','08').group())
print(('[0-9]?[0-9]','888').group())
88
8
08
88
Requirement 4: Matching password (8-20 digits, can be case-sensitive letters, numbers, underscores)
print(('[a-zA-Z0-9_]{8,20}','12345678').group())
print(('[a-zA-Z0-9_]{8}','12345678').group())
12345678
12345678
Matching Boundaries
^: Indicates what it starts with
$: indicates what it ends with
\b: indicates the boundary of the matching word
| or
Requirement 5: Match 163 e-mail address, e-mail user name contains 6 to 18 characters, can be numbers, letters, underscores, but must start with a letter, .
emails='''
awhaldc@
asdasdfddasdfascvdfgbdfgdsds@
afa_@
awhaldc666@
q112dsdasdas@
aaaa_____@
aaaa____@
'''
print(('^[a-zA-Z][\w]{5,17}@163\.com$',emails,).group())
q112dsdasdas@
Requirement 6: Matching word boundaries
print((r'.*\bbeijing\b','I Love beijing too')) print((r'.*\bbeijing\b','I Love beijing1 too')) print((r'.*beijing','I Love beijing too'))
I Love beijing
None
I Love beijing
III. Advanced Usage of the re Module
(pattern,string)
1, findall: pattern in the string of all non-repeating matches, return an iterator iterator saves the matching object
Requirement 7: Match all mailboxes that meet the following criteria
163 e-mail address.
The username of the mailbox contains 6 to 18 characters.
It can be numbers, letters, and underscores,
but it must begin with a letter.
.com ending
import re
emails='''
awhaldc@
asdasdfddasdfascvdfgbdfgdsds@
afa_@
112dsdasdas@
aaaa_____@
aaaa____@
'''
#findall: pattern all non-repeat matches in string, returns an iterator iterator that holds the matches.
list=(r'(^[a-zA-Z][\w]{5,17}@(163|126).com$)',emails,)
print(list)
for email in list:
print(email[0])
[(‘awhaldc@’, ‘163’), (‘aaaa_____@’, ‘126’), (‘aaaa____@’, ‘163’)]
awhaldc@
aaaa_____@
aaaa____@
2、sub：will match to the string, the operation again
Requirement 8: Match a number, home 1 the matched number, return
def add(result): #result is a match
str_num=()
num=int(str_num)+1
return str(num)
print((r'\d+',add,'a=111'))
a=112
3、split：Cut the successful match string
line='hello,world,china.' print((r'\W+',line))
[‘hello’, ‘world’, ‘china’, ‘’]
Requirement 9: Cut strings with colons or spaces.
print((r':| ','info:kobe 18 beijing'))
[‘info’, ‘kobe’, ‘18’, ‘beijing’]
IV. Greedy and non-greedy models
What is the greed model?
Quantifiers in python are greedy by default and always try to match as many characters as possible
What is the non-greedy model?
In contrast to greedy mode, which always tries to match as few characters as possible, you can use, ? , +, {m,n} plus ? , to change greedy mode to non-greedy mode*.
Requirement 9: Non-Greedy Pattern, Requirement: separate the phone call from the descriptive information of the phone call as much as possible, only use regular expressions
line2='this is my phone:188-1111-6666' #Non-greedy pattern, requirement: separate phone calls and phone description information as much as possible, can only use regular expressions result=(r'(.+?)(\d+-\d+-\d+)',line2) print((1)) print((2))
this is my phone:
188-1111-6666
summarize
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