regex

1Regular Expression FUll Cheatsheet (For quick look) :)
2note: for downloading visit https://buggyprogrammer.com/regular-expression-cheatsheet/
3------x-------------------x----------------x------------x----------------x-------------
4
5# -------------- Anchors --------------
6^   →  Start of string, or start of line in multiline pattern
7\A  →  Start of string
8$   →  End of string, or end of line in multi-line pattern
9\Z  →  End of string
10\b  →  Word boundary
11\B  →  Not word boundary
12\<  →  Start of word
13\>  →  End of word
14
15
16# ---------- Character Classes --------
17\c  →  Control character
18\s  →  White space
19\S  →  Not white space
20\d  →  Digit
21\D  →  Not digit
22\w  →  Word
23\W  →  Not word
24\x  →  Hexadecimal digit
25\O  →  Octal digit
26
27
28# --------- Quantifiers -----------------
29*     →    0 or more 
30{3}   →    Exactly 3
31+     →    1 or more 
32{3,}  →    3 or more
33?     →    0 or 1 
34{3,5} →    3, 4 or 5
35Add a ? to a quantifier to make it ungreedy.
36
37
38# ------- Special Characters -------------
39\n   →  New line
40\r   →  Carriage return
41\t   →  Tab
42\v   →  Vertical tab
43\f   →  Form feed
44\xxx →  Octal character xxx
45\xhh →  Hex character hh
46
47
48# --------- Groups and Ranges -------------
49.       →  Any character except new line (\n)
50(a|b)   →  a or b
51(...)   →  Group
52(?:...) →  Passive (non-capturing) group
53[abc]   →  Range (a or b or c)
54[^abc]  →  Not (a or b or c)
55[a-q]   →  Lower case letter from a to q
56[A-Q]   →  Upper case letter from A to Q
57[0-7]   →  Digit from 0 to 7
58\x      →  Group/subpattern number "x"
59Ranges are inclusive.
60
61
62# ----------- Assertions ---------------
63?=         →  Lookahead assertion
64?!         →  Negative lookahead
65?<=        →  Lookbehind assertion
66?!= or ?<! →  Negative lookbehind
67?>         →  Once-only Subexpression
68?()        →  Condition [if then]
69?()|       →  Condition [if then else]
70?#         →  Comment
71
72
73# ------ Pattern Modifiers --------
74g   →  Global match
75i*  →  Case-insensitive
76m*  →  Multiple lines
77s*  →  Treat string as single line
78x*  →  Allow comments and whitespace in pattern
79e*  →  Evaluate replacement
80U*  →  Ungreedy pattern
81*   →  PCRE modifier
82
83
84# ------ String Replacement ------
85$n  →  nth non-passive group
86$2  →  "xyz" in /^(abc(xyz))$/
87$1  →  "xyz" in /^(?:abc)(xyz)$/
88$`  →  Before matched string
89$'  →  After matched string
90$+  →  Last matched string
91$&  →  Entire matched string
92Some regex implementations use \ instead of $
93
94
95# ---------- Escape Sequences ------------
96\ Escape following character
97\Q Begin literal sequence
98\E End literal sequence
99
100"Escaping" is a way of treating characters which have a special meaning in regular
101expressions literally, rather than as special characters.
102
103
104# --------- Common Metacharacters ---------
105^ 
106[
107.
108$
109{
110*
111(
112\
113+
114)
115|
116<
117>
118The escape character is usually \
119
120
121# ------------ POSIX ----------------
122[:upper:]  →  Upper case letters
123[:lower:]  →  Lower case letters
124[:alpha:]  →  All letters
125[:alnum:]  →  Digits and letters
126[:digit:]  →  Digits
127[:xdigit:] →  Hexadecimal digits
128[:punct:]  →  Punctuation
129[:blank:]  →  Space and tab
130[:space:]  →  Blank characters
131[:cntrl:]  →  Control characters
132[:graph:]  →  Printed characters
133[:print:]  →  Printed characters and spaces
134[:word:]   →  Digits, letters and underscore

1Let regex;
2/* shorthand character classes */
3regex = /d/; // matches any digit, short for [0-9]
4regex = /D/; // matches non-digits, short for [^0-9]
5regex = /S/; // matches non-white space character
6regex = /s/; // matches any white space character
7regex = /w/; // matches character, short for [a-zA-Z_0-9]
8regex = /W/; // matches non-word character [^w]
9regex = /b/; // Matches a word boundary where a word character is [a-zA-Z0-9_]
10These meta characters boast a pre-defined meaning and make various typical patterns easier to use.
11/* matching using quantifiers */
12regex= /X./; // matches any character
13regex= /X*/; // Matches zero or several repetitions of letter X, is short for {0,}
14regex= /X+-/; // matches one or more repetitions of letter X, is short for {1,}
15regex= /X?/; // finds no or exactly one letter X, is short for is short for {0,1}.
16regex= // d{3}; // matches three digits. {} describes the order of the preceding liberal
17regex= // d{1,4} ; // means d must occur at least once and at a maximum of four
18A quantifies helps developers to define how often an element occurs.
19/* character ranges */
20regex = /[a-z]/; // matches all lowercase letters
21regex = /[A-Z]/; // matches all uppercase letters
22regex = /[e-l]/; // matches lowercase letters e to l (inclusive)
23regex = /[F-P]/; // matches all uppercase letters F to P (inclusive)
24regex = /[0-9]/; // matches all digits
25regex = /[5-9]/; // matches any digit from 5 to 9 (inclusive)
26regex = / [a-d1-7]/; // matches a letter between a and d and figures from 1 to 7, but not d1
27regex = /[a-zA-Z]/; // matches all lowercase and uppercase letters
28regex = /[^a-zA-Z]/; // matches non-letters
29/* matching using anchors */
30regex = / ^The/; // matches any string that starts with “The”
31regex = / end$/; // matches a string that ends with end
32regex = / ^The end$/; // exact string match starting with “The” and ending with “End”
33/* escape characters */
34regex = / a/; // match a bell or alarm
35regex = / e/; // matches an escape
36regex = / f/; // matches a form feed
37regex = / n/; // matches a new line
38regex = / Q…E/; // ingnores any special meanings in what is being matched
39regex = / r/; // matches a carriage return
40regex = / v/; // matches a vertical tab
41It is critical to note that escape characters are case sensitive
42/* matching using flags */
43regex = / i/; // ignores the case in pattern ( upper and lower case allowed)
44regex = / m/; // multi-line match
45regex = / s/; // match new lines
46regex = / x/; // allow spaces and comments
47regex = / j/; // duplicate group names allowed
48regex = / U/; // ungreedy match

1Let regex;
2/* shorthand character classes */
3regex = /d/; // matches any digit, short for [0-9]
4regex = /D/; // matches non-digits, short for [^0-9]
5regex = /S/; // matches non-white space character
6regex = /s/; // matches any white space character
7regex = /w/; // matches character, short for [a-zA-Z_0-9]
8regex = /W/; // matches non-word character [^w]
9regex = /b/; // Matches a word boundary where a word character is [a-zA-Z0-9_]
10These meta characters boast a pre-defined meaning and make various typical patterns easier to use.
11/* matching using quantifiers */
12regex= /X./; // matches any character
13regex= /X*/; // Matches zero or several repetitions of letter X, is short for {0,}
14regex= /X+-/; // matches one or more repetitions of letter X, is short for {1,}
15regex= /X?/; // finds no or exactly one letter X, is short for is short for {0,1}.
16regex= // d{3}; // matches three digits. {} describes the order of the preceding liberal
17regex= // d{1,4} ; // means d must occur at least once and at a maximum of four
18A quantifies helps developers to define how often an element occurs.
19/* character ranges */
20regex = /[a-z]/; // matches all lowercase letters
21regex = /[A-Z]/; // matches all uppercase letters
22regex = /[e-l]/; // matches lowercase letters e to l (inclusive)
23regex = /[F-P]/; // matches all uppercase letters F to P (inclusive)
24regex = /[0-9]/; // matches all digits
25regex = /[5-9]/; // matches any digit from 5 to 9 (inclusive)
26regex = / [a-d1-7]/; // matches a letter between a and d and figures from 1 to 7, but not d1
27regex = /[a-zA-Z]/; // matches all lowercase and uppercase letters
28regex = /[^a-zA-Z]/; // matches non-letters
29/* matching using anchors */
30regex = / ^The/; // matches any string that starts with “The”
31regex = / end$/; // matches a string that ends with end
32regex = / ^The end$/; // exact string match starting with “The” and ending with “End”
33/* escape characters */
34regex = / a/; // match a bell or alarm
35regex = / e/; // matches an escape
36regex = / f/; // matches a form feed
37regex = / n/; // matches a new line
38regex = / Q…E/; // ingnores any special meanings in what is being matched
39regex = / r/; // matches a carriage return
40regex = / v/; // matches a vertical tab
41It is critical to note that escape characters are case sensitive
42/* matching using flags */
43regex = / i/; // ignores the case in pattern ( upper and lower case allowed)
44regex = / m/; // multi-line match
45regex = / s/; // match new lines
46regex = / x/; // allow spaces and comments
47regex = / j/; // duplicate group names allowed
48regex = / U/; // ungreedy match
49

1Regular expression

1[x for x,y in re.findall(r'((\d)\2+)', '33344555')]
2

1import re
2reload (re)
3
4r = re.compile("([0-9]+)([a-zA-Z]+)([0-9]+)")
5m = r.match("123ab1234")
6if m:
7    print m.group(1)
8    print m.group(2)
9    print m.group(3)
10
11else:
12    print "no match"
13