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

/
/
g

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"(in|out|ref) +w:(\d+) h:(\d+) fmt:(\w+) sar:(\d+)\/(\d+)(?: flags:0x[[:xdigit:]]+)?" test_str = ("ffmpeg version N-86388-g3db98cad5c Copyright (c) 2000-2017 the FFmpeg developers\n" " built with Apple LLVM version 8.1.0 (clang-802.0.42)\n" " configuration: --enable-version3 --enable-gpl --enable-nonfree --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265\n" " libavutil 55. 63.100 / 55. 63.100\n" " libavcodec 57. 96.101 / 57. 96.101\n" " libavformat 57. 72.101 / 57. 72.101\n" " libavdevice 57. 7.100 / 57. 7.100\n" " libavfilter 6. 91.100 / 6. 91.100\n" " libswscale 4. 7.101 / 4. 7.101\n" " libswresample 2. 8.100 / 2. 8.100\n" " libpostproc 54. 6.100 / 54. 6.100\n" "[Parsed_testsrc_0 @ 0x000000000000] size:320x240 rate:25/1 duration:-1.000000 sar:1/1\n" "[Parsed_testsrc_1 @ 0x000000000000] size:640x360 rate:25/1 duration:-1.000000 sar:1/1\n" "[Parsed_scale2ref_2 @ 0x000000000000] w:0 h:trunc((print(ow)*in_h+(in_w*7/2))/(in_h*7))*7 flags:'bilinear' interl:0\n" "Stream mapping:\n" " scale2ref:default -> Stream #0:0 (rawvideo)\n" "Press [q] to stop, [?] for help\n" "[Parsed_testsrc_0 @ 0x000000000000] size:320x240 rate:25/1 duration:-1.000000 sar:1/1\n" "[Parsed_testsrc_1 @ 0x000000000000] size:640x360 rate:25/1 duration:-1.000000 sar:1/1\n" "[Parsed_scale2ref_2 @ 0x7fa20d40efa0] w:0 h:trunc((print(ow)*in_h+(in_w*7/2))/(in_h*7))*7 flags:'bilinear' interl:0\n" "0.000000\n" "[Parsed_scale2ref_2 @ 0x000000000000] The width was set to 0 which will use the width of the reference input (640) not the main input (320).\n" "[Parsed_scale2ref_2 @ 0x000000000000] Consider using: main_w\n" "[Parsed_scale2ref_2 @ 0x000000000000] The height was set to 0 which will use the height of the reference input (360) not the main input (240).\n" "[Parsed_scale2ref_2 @ 0x000000000000] Consider using: main_h\n" "[Parsed_scale2ref_2 @ 0x000000000000] in w:320 h:240 fmt:rgb24 sar:1/1\n" "[Parsed_scale2ref_2 @ 0x000000000000] ref w:640 h:360 fmt:rgb24 sar:1/1\n" "[Parsed_scale2ref_2 @ 0x000000000000] out w:640 h:360 fmt:rgb24 sar:3/4 flags:0x2\n" "Output #0, md5, to 'pipe:':\n" " Stream #0:0: Video: rawvideo, 1 reference frame (RGB[24] / 0x18424752), rgb24, 640x360 [SAR 3:4 DAR 4:3], q=2-31, 138240 kb/s, 25 fps, 25 tbn, 25 tbc (default)\n" " Metadata:\n" " encoder : Lavc rawvideo\n" "No more output streams to write to, finishing.\n" "MD5=cf8c2055d282268025d43c621e468a83\n" "frame= 5 fps=0.0 q=-0.0 Lsize= 0kB time=00:00:00.20 bitrate= 1.5kbits/s speed=7.37x \n" "video:3375kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown\n" "Output file #0 (pipe:):\n" " Output stream #0:0 (video): 5 frames encoded; 5 packets muxed (3456000 bytes); \n" " Total: 5 packets (3456000 bytes) muxed\n") matches = re.finditer(regex, test_str) 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