python-Regular Expressions

Regular expressions that can fetch data

The match is greedy, and the match is more.

>>> Import re

>>> s= "I am years old"

>>> Re.search (r "\d+", s)

<_sre. Sre_match Object at 0x0000000002f63ed0>

>>> Re.search (r "\d+", s). Group ()

' 19 '

>>>

>>> s= "I am years 30"

>>> Re.findall (r "\d", s)

[' 1 ', ' 9 ', ' 2 ', ' 0 ', ' 3 ', ' 0 ']

>>> Re.findall (r "\d+", s)

[' 19 ', ' 20 ', ' 30 ']

Can match data, fetch data,

Determine if the sentence contains a specified string

Re.match (R "\d+", "123ABC") inside R preferably with, to prevent escape character effects

R "\d" match numbers

>>> Re.match (r "\d+", "123ABC")

<_sre. Sre_match Object at 0x0000000002f63ed0>

>>> Re.match ("\d+", "123ABC")

<_sre. Sre_match Object at 0x000000000306b030>

>>> Re.match ("\d+", "A123ABC")

>>> Re.match ("\d+", "A123ABC")

>>> Re.match ("\d+", "123ABC"). Group ()

' 123 '

>>> Re.match ("\d+", "123abc 1SD"). Group ()

' 123 '

Re.search (r "\d+") any position conforming to return Re.findall (r "\d+"), and any position matching will return Re.match (r "\d+"), starting from the first position of the string to match

>>> Re.match ("\d+", "123abc 1SD"). Group ()

' 123 '

>>> re.search ("\d+", "123abc 1SD"). Group ()

' 123 '

>>> re.search ("\d+", "A123abc 1SD"). Group ()

' 123 '

>>> Re.match ("\d+", "A123abc 1SD"). Group ()

Traceback (most recent):

File "<stdin>", line 1, in <module>

Attributeerror: ' Nonetype ' object has no attribute ' group '

>>> Re.match ("\d+", "A123abc 1SD")

>>> Re.findall (r "\d+", "A1B2C3")

[' 1 ', ' 2 ', ' 3 ']

>>> Re.match (r "\d+", "A1B2C3")

R "\d" matches non-numeric re.match (r "\d+", "a1b2c3") matches non-numeric

>>> Re.match (r "\d+", "A1B2C3"). Group ()

A

>>> Re.match (r "\d+", "ABC1B2C3"). Group ()

' ABC '

Re.match (R "\d+\d+", "AB12 BB"). Group () matches "AB12 BB", matching AB12

>>> Re.match (r "\d+\d+", "AB12 BB"). Group ()

' Ab12 '

R "\s" matches white space Re.match (r "\s+", "s") matches white space, match function starts matching from the first character of a string

>>> Re.match (r "\s+", "AB12 BB"). Group ()

Traceback (most recent):

File "<stdin>", line 1, in <module>

Attributeerror: ' Nonetype ' object has no attribute ' group '

>>> Re.match (r "\s+", "BB"). Group ()

R "\s" matches non-blank Re.match (r "\s+", "eee BB") non-whitespace until white space appears

>>> Re.match (r "\s+", "eee BB"). Group ()

' EE

>>> print ' A ' #str方法

A

>>> ' A ' #repr方法

A

R "\w+" matches numbers and letters Re.findall (r "\w+", "SDF") numbers and letters

>>> Re.findall (r "\w+", "SDF")

[' SDF ']

>>> Re.findall (r "\w+", "SDF")

[' A ', ' SDF ']

>>> Re.findall (r "\w+", "SDF we")

[' A ', ' SDF ', ' we ']

R "\w+" matches non-numeric and non-alphabetic Re.match (R "\w+", "SF FD"). Group () non-numeric and non-alphabetic

>>> Re.match (r "\w+", "SF FD"). Group ()

‘ ‘

>>> Re.match (r "\w+", "SF $% @# FD"). Group ()

‘ ‘

>>> Re.match (r "\w+", "$#% SF $% @# FD"). Group ()

' $#% '

Quantifiers

R "\w\w" Fetch two

>>> Re.match (r "\w\w", "ww we"). Group ()

' WW '

>>> Re.match (r "\w\w", "we"). Group ()

' 12 '

R "\w{2}" fetch two

>>> Re.match (r "\w{2}", "we"). Group ()

' 12 '

>>> Re.match (r "\w{2}", "123 we"). Group ()

' 12 '

>>> Re.match (r "\w{2}", "1"). Group ()

Traceback (most recent):

File "<stdin>", line 1, in <module>

Attributeerror: ' Nonetype ' object has no attribute ' group '

>>> Re.match (r "\w{2,4}", "1"). Group ()

Traceback (most recent):

File "<stdin>", line 1, in <module>

Attributeerror: ' Nonetype ' object has no attribute ' group '

R "\w{2,4}", Fetch 2 to 4, by most matches

>>> Re.match (r "\w{2,4}", "123 we"). Group ()

' 123 '

>>> Re.match (r "\w{2,4}", "we"). Group ()

' 12 '

>>> Re.match (r "\w{2,4}", "123 we"). Group ()

' 123 '

>>> Re.match (r "\w{2,4}", "1235 we"). Group ()

' 1235 '

>>> Re.match (r "\w{2,4}", "12435 we"). Group ()

' 1243 '

>>> Re.match (r "\w{5}", "12435 we"). Group ()

' 12435 '

>>> Re.match (r "\w{5}", "Srsdf we"). Group ()

' Srsdf '

>>>

R "\w{2,4}?" Suppress greed, by least match

>>> Re.match (r "\w{2,4}?", "12435 we"). Group ()

' 12 '

R "\w?" Match 0 times and once, if there is no match, return null

0 Times is also a match,

>>> Re.match (r "\w", "12435 we"). Group ()

' 1 '

>>> Re.match (r "\w", "12435 we"). Group ()

‘‘

Re.findall (r "\w?", "we") match to the last, nothing, 0 times, return empty

>>> Re.findall (r "\w", "we")

[' ', ' 1 ', ' 2 ', ', ' w ', ' e ', ']

Re.findall (R "\w", "we") matches a

>>> Re.findall (r "\w", "we") matches a

[' 1 ', ' 2 ', ' W ', ' e ']

R "\w*" matches 0 or more times

>>> Re.match (r "\w*", "12435 we"). Group ()

‘‘

>>> Re.match (r "\w*", "12435 we"). Group ()

' 12435 '

>>> Re.match (r "\w*", "12435 we")

<_sre. Sre_match Object at 0x0000000002f63ed0>

>>> Re.match (r "\w*", "12435 we")

<_sre. Sre_match Object at 0x000000000306c030>

>>> Re.match (r "\w*", "12435 we"). Group ()

' 12435 '

R "a.b" matches any character except carriage return between AB

If you want to match "A.B", use R "a\.b"

>>> Re.match (r "a.b", "AXB")
<_sre. Sre_match Object at 0x0000000001dcc510>
>>> Re.match (r "a.b", "A\NB")
>>> Re.match (r "a\.b", "a.b")
<_sre. Sre_match Object at 0x00000000022be4a8>
>>> Re.match (r "a\.b", "AXB")

>>> Re.match (R ".", "AXB"). Group ()
A
>>> Re.match (r "a.b", "AXB"). Group ()
' Axb '

Practice matching this IP address, the rule is there are 3. and 4 segments, numbers from 0 to 255, you can

S= "I find a ip:1.2.22.123! Yes

>>>re.search (r "\d{1,3}\.\d{1,3}\.\d{1,3}.\d{1,3}", s). Group ()

' 1.2.22.123 '

Re.search (R "(\d{1,3}\.) {3}\d{1,3} ", s) group match

>>>re.search (R "(\d{1,3}\.) {3}\d{1,3} ", s). Group ()

' 1.2.22.123 '

>>> Re.search (R "(\d{1,3}\.) {3}\d{1,3} ", s). Group ()
' 1.2.22.123

Match related formats for multiple characters
Character function
* Match the previous characters appear 0 times or the limit of the time, you can have?
+ 1 occurrences of pre-match characters or a limit of 1 times
? Matches the previous character 1 or 0 times, that is, either 1 times or no
{m} matches previous characters appear m times
{m,} matches the previous character? Less than m times
{M,n} matches before a character appears from M to N times

Character function
. Matches any of 1 characters (except \ n)
[] matches the characters enumerated in []
\d match number, i.e. 0-9
\d match? Numbers, i.e. not numbers
\s match empty, that is, the Space, TAB key
\s match? Empty?
\w matches word characters, i.e. A-Z, A-Z, 0-9, _
\w match? Word character

python-Regular Expressions