Regular Record of 23 June 2018

Regular Basic Grammar

grammar	Explain	EXAMPLES OF EXPRESSIONS	Complete matching
.	Match any character	a.c	abc
\	Escape character	a\.c	a.c
[]	character set	a[bcd]e	abe/ace/ade
\d	Number: [0-9]	a\dc	a1c
\D	Non-numeric: [^\ d]	a\Dc	abc
\s	Blank characters: [<Blank>]\trn\f\v	a\sc	a c
*	Match Fist A Character 0 or infinite times	abc*	ab/abccc
+	Match the previous character 1 or infinitely	abc*	abc/abccc
?	Match the previous character 0 or 1 times	abc?	ab/abc
\w	Word character [A-Za-z0-9_]	a\wc	abc
{m}	Match the previous character m times	ab{2}c	abbc
( )	Matching expressions in parentheses also represents a group

re.match

Trying to match a pattern from the actual position of the string, returning none if the match is not successful

Conventional matching:

import re
content="Hello 123 456 World is a houzi"
result = re.match("^Hello\s\d\d\d\s\d\d\d\s\w.*houzi$",content)
print(result.group())
print(result)
print(result.span())

#Return results
>>>Hello 123 456 World is a houzi
>>><_sre.SRE_Match object; span=(0, 30) >>>match='Hello 123 456 World is a houzi'>
>>>(0, 30)

Universal Matching: * Matching any arbitrary character

import re
content="Hello 123 456 World is a houzi"
result = re.match("^Hello.*houzi$",content)
print(result.group())
print(result)
print(result.span())

# Return results
>>>Hello 123 456 World is a houzi
>>><_sre.SRE_Match object; span=(0, 30)
>>>match='Hello 123 456 World is a houzi'>
>>>(0, 30)

Matching target:

import re
content="Hello 123 456 World is a houzi"
result = re.match("^Hello\s(\d+)\s.*houzi$",content)
print(result.group(1))
print(result)
print(result.span())

# Output results
>>> 123
>>> <_sre.SRE_Match object; span=(0, 30)
>>> match='Hello 123 456 World is a houzi'>
>>> (0, 30)

Greed Matches:

* Match as many characters as possible

import re
content="Hello 123 456 World is a houzi"
result = re.match("^Hello.*(\d+)\s.*houzi$",content)
print(result.group(1))
print(result)
print(result.span())
# Output results
>>> 6  # 123 45 is all matched.
>>> <_sre.SRE_Match object; span=(0, 30)
>>> match='Hello 123 456 World is a houzi'>
>>> (0, 30)

Non-greedy matching:

Match as few characters as possible

import re
content="Hello 123 456 World is a houzi"
result = re.match("^Hello.*?(\d+)\s.*houzi$",content)
print(result.group(1))
print(result)
print(result.span())
#Output results
>>> 123  # * Stop when only numbers are matched
>>> <_sre.SRE_Match object; span=(0, 30)
>>> match='Hello 123 456 World is a houzi'>
>>> (0, 30)

Matching mode:

import re
content="Hello 123 456 World \n is a houzi"
result = re.match("^Hello.*?(\d+).*houzi$",content,re.S)
# re.S enables. * to match special characters
print(result.group(1))
print(result)
print(result.span())
# Output results
123
<_sre.SRE_Match object; span=(0, 32), match='Hello 123 456 World \n is a houzi'>
(0, 32)

Transliteration:

Add escape before special symbols

import re
content="Hello $5.00"
result = re.match("Hello \$5\.00",content)
print(result.group())
print(result.span())

re.search

Search the entire string and return the first successful match

import re
content="Hello $5.00"
result = re.search("(Hello)",content)
print(result.group())
print(result.span())
# Output results
>>> Hello
>>> (0, 5)

Findall (Find all)

Search for strings and return all matchable substrings in list form

ret = re.findall("Matching rules",Matching object)
# The return is a list

re.findall(".","\n",re.S)
#re.S can match newline characters

Re.sub (replacement)

Replace each matching substring in the string and return the replaced string

import re
content="Hello $5.00"
result = re.sub("(Hello)","shut!",content)
print(result)
# Output results
>>> shut! $5.00

import re
content="Hello $5.00"
# R "1 shut!" means to get the first group of matches.
result = re.sub("(Hello)",r"\1 shut!",content)
print(result)

# Output results
>>> Hello shut! $5.00

You can use sub

import re
content="<a src='www.baidu.com'></a>" \
        "<li>ssss</li>"
result = re.sub("<a.*?></a>","",content)
print(result)
# Output results
>>> <li>ssss</li>

Compile

Compiling regular strings into regular objects to facilitate reuse and change matching patterns

import re
content="<a src='www.baidu.com'></a>" \
        "<li>ssss</li>"
pattern = re.compile("<a.*?></a>",re.S)
result = re.match(pattern,content)
print(type(pattern))
print(result.group())

# Output results
<class '_sre.SRE_Pattern'>
<a src='www.baidu.com'></a>

Finally, regular work is really used more, or study hard, has been constantly beyond their own. The first article to this bar

Posted by inkfish on Fri, 23 Aug 2019 04:36:32 -0700

Programmer Group