Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
Processing...

Test String

Substitution
Processing...

Code Generator

Language

Generated Code

import re regex = re.compile(r""" (\w+)\.(\w+)? """, flags=re.UNICODE | re.MULTILINE | re.IGNORECASE | re.VERBOSE) test_str = ("a[a]=20&a[]=21\n" "a.a=20&a.=21\n\n" "a[77]=20&a[]=21\n" "a.77=20&a.=21\n\n" "a[]=19&a[77]=20&a[]=21\n" "a.=19&a.77=20&a.=21\n\n" "a[b][]=1&a[b][]=2&a[b]=3&a[b][]=4\n" "a.b.=1&a.b.=2&a.b=3&a.b.=4\n\n" "a[][]=20&a[][]=21\n" "a..=20&a..=21\n\n" "a[]=10&a[][]=20&a[][]=21\n" "a.=10&a..=20&a..=21") subst = "\\1[\\2]" result = regex.sub(subst, test_str) if result: print(result)

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Python, please visit: https://docs.python.org/3/library/re.html