Regular Expressions 101

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Function

  • Match
  • Substitution
  • List
  • Unit Tests (10)

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An explanation of your regex will be automatically generated as you type.
  • 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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

r"
"
xgm

Unit Tests

given the string FBar assert that capture group 2 equals Bar
given the string FBar assert that capture group 1 equals F
given the string FooBarBaz assert that capture group 2 equals BarBaz
given the string FooBarBaz assert that capture group 1 equals Foo
given the string FOOBar assert that capture group 2 equals Bar
given the string FOOBar assert that capture group 1 equals FOO
given the string FooBar assert that capture group 2 equals Bar
given the string FooBar assert that capture group 1 equals Foo
given the string fooBar assert that capture group 2 equals Bar
given the string fooBar assert that capture group 1 equals foo

Code Generator

Language

Generated Code

# coding=utf8 # the above tag defines encoding for this document and is for Python 2.x compatibility import re regex = r""" ^ ( # Match one of these: [A-Z]?[a-z]+| # A possibly-capitalized identifier, or: [A-Z]+ # An ALL CAPS identifier... (?![a-z]) # ...not immediately followed by lowercase ) # and capture the rest of the string (.*?) $ """ test_str = "" matches = re.finditer(regex, test_str, re.VERBOSE | re.MULTILINE) for matchNum, match in enumerate(matches, start=1): print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group())) for groupNum in range(0, len(match.groups())): groupNum = groupNum + 1 print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum))) # Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.

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