regex
Let regex;
/* shorthand character classes */
regex = /d/; // matches any digit, short for [0-9]
regex = /D/; // matches non-digits, short for [^0-9]
regex = /S/; // matches non-white space character
regex = /s/; // matches any white space character
regex = /w/; // matches character, short for [a-zA-Z_0-9]
regex = /W/; // matches non-word character [^w]
regex = /b/; // Matches a word boundary where a word character is [a-zA-Z0-9_]
These meta characters boast a pre-defined meaning and make various typical patterns easier to use.
/* matching using quantifiers */
regex= /X./; // matches any character
regex= /X*/; // Matches zero or several repetitions of letter X, is short for {0,}
regex= /X+-/; // matches one or more repetitions of letter X, is short for {1,}
regex= /X?/; // finds no or exactly one letter X, is short for is short for {0,1}.
regex= // d{3}; // matches three digits. {} describes the order of the preceding liberal
regex= // d{1,4} ; // means d must occur at least once and at a maximum of four
A quantifies helps developers to define how often an element occurs.
/* character ranges */
regex = /[a-z]/; // matches all lowercase letters
regex = /[A-Z]/; // matches all uppercase letters
regex = /[e-l]/; // matches lowercase letters e to l (inclusive)
regex = /[F-P]/; // matches all uppercase letters F to P (inclusive)
regex = /[0-9]/; // matches all digits
regex = /[5-9]/; // matches any digit from 5 to 9 (inclusive)
regex = / [a-d1-7]/; // matches a letter between a and d and figures from 1 to 7, but not d1
regex = /[a-zA-Z]/; // matches all lowercase and uppercase letters
regex = /[^a-zA-Z]/; // matches non-letters
/* matching using anchors */
regex = / ^The/; // matches any string that starts with “The”
regex = / end$/; // matches a string that ends with end
regex = / ^The end$/; // exact string match starting with “The” and ending with “End”
/* escape characters */
regex = / a/; // match a bell or alarm
regex = / e/; // matches an escape
regex = / f/; // matches a form feed
regex = / n/; // matches a new line
regex = / Q…E/; // ingnores any special meanings in what is being matched
regex = / r/; // matches a carriage return
regex = / v/; // matches a vertical tab
It is critical to note that escape characters are case sensitive
/* matching using flags */
regex = / i/; // ignores the case in pattern ( upper and lower case allowed)
regex = / m/; // multi-line match
regex = / s/; // match new lines
regex = / x/; // allow spaces and comments
regex = / j/; // duplicate group names allowed
regex = / U/; // ungreedy match
4.33
3
import re
reload (re)
r = re.compile("([0-9]+)([a-zA-Z]+)([0-9]+)")
m = r.match("123ab1234")
if m:
print m.group(1)
print m.group(2)
print m.group(3)
else:
print "no match"
Thank you!
3
0
4.33
3
Let regex;
/* shorthand character classes */
regex = /d/; // matches any digit, short for [0-9]
regex = /D/; // matches non-digits, short for [^0-9]
regex = /S/; // matches non-white space character
regex = /s/; // matches any white space character
regex = /w/; // matches character, short for [a-zA-Z_0-9]
regex = /W/; // matches non-word character [^w]
regex = /b/; // Matches a word boundary where a word character is [a-zA-Z0-9_]
These meta characters boast a pre-defined meaning and make various typical patterns easier to use.
/* matching using quantifiers */
regex= /X./; // matches any character
regex= /X*/; // Matches zero or several repetitions of letter X, is short for {0,}
regex= /X+-/; // matches one or more repetitions of letter X, is short for {1,}
regex= /X?/; // finds no or exactly one letter X, is short for is short for {0,1}.
regex= // d{3}; // matches three digits. {} describes the order of the preceding liberal
regex= // d{1,4} ; // means d must occur at least once and at a maximum of four
A quantifies helps developers to define how often an element occurs.
/* character ranges */
regex = /[a-z]/; // matches all lowercase letters
regex = /[A-Z]/; // matches all uppercase letters
regex = /[e-l]/; // matches lowercase letters e to l (inclusive)
regex = /[F-P]/; // matches all uppercase letters F to P (inclusive)
regex = /[0-9]/; // matches all digits
regex = /[5-9]/; // matches any digit from 5 to 9 (inclusive)
regex = / [a-d1-7]/; // matches a letter between a and d and figures from 1 to 7, but not d1
regex = /[a-zA-Z]/; // matches all lowercase and uppercase letters
regex = /[^a-zA-Z]/; // matches non-letters
/* matching using anchors */
regex = / ^The/; // matches any string that starts with “The”
regex = / end$/; // matches a string that ends with end
regex = / ^The end$/; // exact string match starting with “The” and ending with “End”
/* escape characters */
regex = / a/; // match a bell or alarm
regex = / e/; // matches an escape
regex = / f/; // matches a form feed
regex = / n/; // matches a new line
regex = / Q…E/; // ingnores any special meanings in what is being matched
regex = / r/; // matches a carriage return
regex = / v/; // matches a vertical tab
It is critical to note that escape characters are case sensitive
/* matching using flags */
regex = / i/; // ignores the case in pattern ( upper and lower case allowed)
regex = / m/; // multi-line match
regex = / s/; // match new lines
regex = / x/; // allow spaces and comments
regex = / j/; // duplicate group names allowed
regex = / U/; // ungreedy match
Thank you!
3
0
3.75
4
REGEXP is a pattern match in which matches pattern anywhere in the search value.
Thank you!
4
0
3
1
import re
# The string you want to find a pattern within
test_string = 'Hello greppers!'
# Creating a regular expression pattern
# This is a simple one which finds "Hello"
pattern = re.compile(r'Hello')
# This locates and returns all the occurences of the pattern
# within the test_string
match = pattern.finditer(test_string)
# Outputs all the ocurrences which were returned as
# as match objects
for match in matches:
print(match)
Thank you!
1
0
3.5
6
Regular Expression FUll Cheatsheet (For quick look) :)
note: for downloading visit https://buggyprogrammer.com/regular-expression-cheatsheet/
------x-------------------x----------------x------------x----------------x-------------
# -------------- Anchors --------------
^ → Start of string, or start of line in multiline pattern
\A → Start of string
$ → End of string, or end of line in multi-line pattern
\Z → End of string
\b → Word boundary
\B → Not word boundary
\< → Start of word
\> → End of word
# ---------- Character Classes --------
\c → Control character
\s → White space
\S → Not white space
\d → Digit
\D → Not digit
\w → Word
\W → Not word
\x → Hexadecimal digit
\O → Octal digit
# --------- Quantifiers -----------------
* → 0 or more
{3} → Exactly 3
+ → 1 or more
{3,} → 3 or more
? → 0 or 1
{3,5} → 3, 4 or 5
Add a ? to a quantifier to make it ungreedy.
# ------- Special Characters -------------
\n → New line
\r → Carriage return
\t → Tab
\v → Vertical tab
\f → Form feed
\xxx → Octal character xxx
\xhh → Hex character hh
# --------- Groups and Ranges -------------
. → Any character except new line (\n)
(a|b) → a or b
(...) → Group
(?:...) → Passive (non-capturing) group
[abc] → Range (a or b or c)
[^abc] → Not (a or b or c)
[a-q] → Lower case letter from a to q
[A-Q] → Upper case letter from A to Q
[0-7] → Digit from 0 to 7
\x → Group/subpattern number "x"
Ranges are inclusive.
# ----------- Assertions ---------------
?= → Lookahead assertion
?! → Negative lookahead
?<= → Lookbehind assertion
?!= or ?<! → Negative lookbehind
?> → Once-only Subexpression
?() → Condition [if then]
?()| → Condition [if then else]
?# → Comment
# ------ Pattern Modifiers --------
g → Global match
i* → Case-insensitive
m* → Multiple lines
s* → Treat string as single line
x* → Allow comments and whitespace in pattern
e* → Evaluate replacement
U* → Ungreedy pattern
* → PCRE modifier
# ------ String Replacement ------
$n → nth non-passive group
$2 → "xyz" in /^(abc(xyz))$/
$1 → "xyz" in /^(?:abc)(xyz)$/
$` → Before matched string
$' → After matched string
$+ → Last matched string
$& → Entire matched string
Some regex implementations use \ instead of $
# ---------- Escape Sequences ------------
\ Escape following character
\Q Begin literal sequence
\E End literal sequence
"Escaping" is a way of treating characters which have a special meaning in regular
expressions literally, rather than as special characters.
# --------- Common Metacharacters ---------
^
[
.
$
{
*
(
\
+
)
|
<
>
The escape character is usually \
# ------------ POSIX ----------------
[:upper:] → Upper case letters
[:lower:] → Lower case letters
[:alpha:] → All letters
[:alnum:] → Digits and letters
[:digit:] → Digits
[:xdigit:] → Hexadecimal digits
[:punct:] → Punctuation
[:blank:] → Space and tab
[:space:] → Blank characters
[:cntrl:] → Control characters
[:graph:] → Printed characters
[:print:] → Printed characters and spaces
[:word:] → Digits, letters and underscore
Thank you!
6
0
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