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

~
~
sxg

Test String

Code Generator

Generated Code

# coding=utf8 # the above tag defines encoding for this document and is for Python 2.x compatibility import re regex = r""" (?(DEFINE) # Start of definitions (?P<str_double_quotes> (?<!\\) # Not escaped " # Match a double quote (?: # Non-capturing group [^\\] # Match anything not a backslash | # Or \\. # Match a backslash and a single character (ie: an escaped character) )*? # Repeat the non-capturing group zero or more times, ungreedy/lazy " # Match the ending double quote ) (?P<str_single_quotes> (?<!\\) # Not escaped ' # Match a single quote (?: # Non-capturing group [^\\] # Match anything not a backslash | # Or \\. # Match a backslash and a single character (ie: an escaped character) )*? # Repeat the non-capturing group zero or more times, ungreedy/lazy ' # Match the ending single quote ) (?P<brackets> \( # Match an opening bracket (?: # A non capturing group (?&str_double_quotes) # Recurse/use the str_double_quotes pattern | # Or (?&str_single_quotes) # Recurse/use the str_single_quotes pattern | # Or [^()] # Anything not a bracket | # Or (?&brackets) # Recurse the bracket pattern )* \) ) ) # End of definitions # Let's start matching for real now: _n? # Match _ or _n \s* # Optional white spaces (?P<results>(?&brackets)) # Recurse/use the brackets pattern and put it in the results group """ test_str = ("_ (\"foo\") // want \"foo\"\n" "_n(\"bar\", \"baz\", 42); // want \"bar\", \"baz\", 42\n" "_n(domain, \"bux\", var); // want domain, \"bux\", var\n" "_( \"one (optional)\" ); // want \"one (optional)\"\n" "apples === 0 ? _( \"No apples\" ) : _n(\"%1 apple\", \"%1 apples\", apples) // could have on the same line two calls..\n\n" "// misleading cases\n" "_n(\"foo (\")\n" "_n(\"foo (\\)\", 'foo)', aa)\n" "_n( Array(1, 2, 3), Array(\")\", '(') );\n" "_n(function(foo){return foo*2;}); // Is this even valid?\n" "_n (); // Empty\n" "_ ( \n" " \"Foo\",\n" " 'Bar',\n" " Array(\n" " \"wow\",\n" " \"much\",\n" " 'whitespaces'\n" " ),\n" " multiline\n" "); // PCRE is awesome") matches = re.finditer(regex, test_str, re.DOTALL | re.VERBOSE) 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