Python Regular Expression Basics

#1 character Matching

Import re

R=r ' AB '

Print Re.findall (R, ' ABCDEFGABCD ')

#2 If you have metacharacters, be aware that you use the escape character ' \ '

R=r ' 1\*2 '

Print Re.findall (R, ' 01*234501*2345 ')

#元字符介绍

#3 ^ Match beginning of Line

R=r ' ^123 '

Print Re.findall (R, ' 1234512345 ')

#4 $ match Line end

R=r ' 345$ '

Print Re.findall (R, ' 1234512345 ')

#5. Match single character

R=r ' 3.5 '

Print Re.findall (R, ' 1234512345 ')

#6 [] matches a specified character set

R=r ' A[a-za-z0-9]c '

Print Re.findall (R, ' Abc,acc,a5c,a3c,cfg ')

#7 [^] complement matches characters that are not in range, note ^ put in front

R=r ' A[^0-9]c '

Print Re.findall (R, ' Abc,acc,a5c,a3c,cfg ')

#特殊意义字符

#8 \d representative number [0-9]

R=r ' A\DC '

Print Re.findall (R, ' Abc,acc,a5c,a3c,cfg ')

#9 \d Non-digital

R=r ' A\DC '

Print Re.findall (R, ' Abc,acc,a5c,a3c,cfg ')

#10 \s whitespace characters

R=r ' A\SC '

Print Re.findall (R, ' Abc,acc,a5c,a3c,cfg,a c,a C ')

#11 \s non-whitespace characters

R=r ' A\SC '

Print Re.findall (R, ' Abc,acc,a5c,a3c,cfg,a c,a C ')

#12 \w word character [a-za-z0-9_]

R=r ' A\WC '

Print Re.findall (R, ' Abc,acc,a5c,a3c,cfg,a c,a c,a_c ')

#13 \w non-word characters

R=r ' A\WC '

Print Re.findall (R, ' Abc,acc,a5c,a3c,cfg,a c,a c,a_c ')

#14 {} The number of repetitions of the previous character

R=r ' A{2}c '

Print Re.findall (R, ' 1AAC,2AACC,3AAAAAC ')

#15 the number of repetitions of the previous character within a range

R=r ' A{1,4}c '

Print Re.findall (R, ' AC,AACC,AAAAAC ')

#16 * Match the previous character by more than or equal to 0 times, {0,} effect equivalent to *

R=r ' 1[a]*c '

Print Re.findall (R, ' 1c2,1aacc2,1aaaaac2 ')

#17 + matches the previous character more than or equal to 1 times, {1,} effect equivalent to +

R=r ' 1[a]+c '

Print Re.findall (R, ' 1c2,1aacc2,1aaaaac2 ')

#18? Match the previous character 0 or 1 times to indicate whether the {0,1} effect is equivalent to?

R=r ' 1[ab]?c '

Print Re.findall (R, ' 1C,1AC2,1BC2,1ABC2 ')

#19 *? Match as few as possible

R=r ' 1.*?c '

Print Re.findall (R, ' 1abc1,1abc1,c ')

#20 () grouping, note that the ' \.com\.cn ' is placed in front, the whole plus parentheses as a large grouping to easily see which matches to which

R=r ' (\[email protected]\w+ (\.com\.cn|\.com|\.cn)) '

Print Re.findall (r, ' [email protected] ')

The results of the operation are as follows:

>>>

1 [' AB ', ' AB ']

2 [' 1*2 ', ' 1*2 ']

3 [' 123 ']

4 [' 345 ']

5 [' 345 ', ' 345 ']

6 [' abc ', ' ACc ', ' a5c ', ' a3c ']

7 [' abc ', ' ACc ']

8 [' a5c ', ' a3c ']

9 [' abc ', ' ACc ']

Ten [' A C ']

One [' abc ', ' ACc ', ' a5c ', ' a3c ']

[' abc ', ' ACc ', ' a5c ', ' a3c ', ' A_c ']

[' A C ']

[' AAC ', ' AAC ', ' AAC ']

[' AC ', ' aac ', ' AAAAC ']

[' 1c ', ' 1AAC ', ' 1AAAAAC ']

[' 1aac ', ' 1AAAAAC ']

[' 1c ', ' 1ac ', ' 1BC ']

[' 1abc ', ' 1,1abc ', ' 1,c ']

[(' [email protected] ', '. com.cn ')]

>>>

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Python Regular Expression Basics