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
No Match

r"
"
mg

Test String

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"^(\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.\d{3}(?:Z|[+-]\d{2}:\d{2}))\s*(\w+)\s*(\d*)\s*---\s*\[\s*([a-zA-Z0-9\._-]+)?\]\s*([^\s]+)\s*:\s*([^\n]+)$" test_str = ("2023-02-13T20:51:06.372+05:30 INFO 28357 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication using Java 17.0.2 with PID 28357 (/Users/snehangshub/Documents/Experiments/demo/build/classes/java/main started by snehangshub in /Users/snehangshub/Documents/Experiments/demo)\n" "2023-02-13T20:51:06.373+05:30 INFO 28357 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to 1 default profile: \"default\"\n" "2023-02-13T20:51:06.715+05:30 INFO 28357 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)\n" "2023-02-13T20:51:06.721+05:30 INFO 28357 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]\n" "2023-02-13T20:51:06.721+05:30 INFO 28357 --- [ main] o.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/10.1.5]\n" "2023-02-13T20:51:06.763+05:30 INFO 28357 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext\n" "2023-02-13T20:51:06.764+05:30 INFO 28357 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 371 ms\n" "2023-02-13T20:51:06.899+05:30 INFO 28357 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''\n" "2023-02-13T20:51:06.903+05:30 INFO 28357 --- [ main] com.example.demo.DemoApplication : Started DemoApplication in 0.684 seconds (process running for 0.832)\n" "2023-02-13T20:51:24.855+05:30 INFO 28357 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'\n" "2023-02-13T20:51:24.855+05:30 INFO 28357 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'\n" "2023-02-13T20:51:24.858+05:30 INFO 28357 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 2 ms\n" "2023-02-13T19:09:07.379Z INFO 1 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''") matches = re.finditer(regex, test_str, 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