Regular Expressions 101

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Function

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  • Unit Tests (1)
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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

Code Generator

Language

Generated Code

import re regex = re.compile(r"^(0|[1-9][0-9]*)(e-?(0|[1-9][0-9]*))?$", flags=re.MULTILINE) test_str = ("0\n" "1\n" "-0\n" "-1\n" "+0\n" "+1\n" "01\n" "-01\n" "+01\n\n" "2.3\n" "-2.3\n" "1.00\n" "0.00\n" "-0.00\n" "00.00\n" "-00.00\n" "02.3\n" ".0\n" ".1\n" "-.1\n" "0.\n" "1.\n" "10.\n" "2,3\n" ",0\n\n" "0e0\n" "2e5\n" "-e10\n" "-e-10\n" "2.3e5\n" "-2.3e5\n" "2.3e-5\n" "2.3e03\n" "2.3e0\n" "0.01e4\n" ".1e5\n" "-.1e5\n" "-.0e0\n" "-0.0e10\n" "2,3e5\n" " \n" ".\n" "-\n" "-.\n" "b1\n" "1b\n" "2-3\n" "3.4.5\n" "4.,6\n" "1,.\n" "e\n" "-e\n" "-.e\n" ".e4\n" "1e2-2\n" "e2.3\n" "e2.3.4\n" "-e10\n" "1e.-\n" "10e.\n" "1\\n\n" "1\\t\n" "1 1\n" "\\n\n" "\\t\n") matches = regex.finditer(test_str) for match_num, match in enumerate(matches, start=1): print(f"Match {match_num} was found at {match.start()}-{match.end()}: {match.group()}") for group_num, group in enumerate(match.groups(), start=1): print(f"Group {group_num} found at {match.start(group_num)}-{match.end(group_num)}: {group}")

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