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"
"
gm

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"^(.*ext[2-4]|.*xfs)(\s+)((([a-zA-Z\=\-]+)(?!noatime,nodireatime)).+)" test_str = ("# Not match\n" "/dev/mapper/VolGroup00-root / ext4 errors=remount-ro,noatime,nodiratime 0 1\n" "/dev/mapper/VolGroup00-home /home ext4 defaults,noatime,nodiratime 0 2\n" "LABEL=cloudimg-rootfs / ext4 defaults,noatime,nodiratime 0 0\n\n" "# /etc/fstab: static file system information.\n" "#\n" "# Use 'blkid' to print the universally unique identifier for a\n" "# device; this may be used with UUID= as a more robust way to name devices\n" "# that works even if disks are added and removed. See fstab(5).\n" "#\n" "# <file system> <mount point> <type> <options> <dump> <pass>\n" "/dev/mapper/VolGroup00-root / ext4 errors=remount-ro 0 1\n" "# /boot was on /dev/sda1 during installation\n" "UUID=72836e37-44d4-4612-90ef-0e545a0071a6 /boot ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-home /home ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-tmp /tmp ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-var /var ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-swap_1 none swap sw 0 0\n" "/dev/fd0 /media/floppy0 auto rw,user,noauto,exec,utf8 0 0\n\n" "# Ubuntu OpenStack\n" "LABEL=cloudimg-rootfs / ext4 defaults 0 0\n\n\n" "# Centos\n" "/dev/mapper/VolGroup00-lv_slash / xfs defaults 0 0\n" "UUID=4534700a-a2b2-4d6c-9415-c372da0c39eb /boot xfs defaults 0 0\n" "/dev/mapper/VolGroup00-lv_home /home xfs defaults 0 0\n" "/dev/mapper/VolGroup00-lv_tmp /tmp xfs defaults 0 0\n" "/dev/mapper/VolGroup00-lv_var /var xfs defaults 0 0\n" "/dev/mapper/VolGroup00-lv_swap swap swap defaults 0 0\n\n" "# Debian 7\n" "/dev/mapper/VolGroup00-root / ext4 errors=remount-ro 0 1\n" "# /boot was on /dev/sda1 during installation\n" "UUID=080670e3-93d1-4fdc-be7d-d8b05ad6d1e5 /boot ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-home /home ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-tmp /tmp ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-var /var ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-swap_1 none swap sw 0 0\n" "/dev/sr0 /media/cdrom0 udf,iso9660 user,noauto 0 0\n" "/dev/fd0 /media/floppy0 auto rw,user,noauto 0 0\n\n\n\n" "# Debian 8\n" "/dev/mapper/VolGroup00-root / ext4 errors=remount-ro 0 1\n" "# /boot was on /dev/sda1 during installation\n" "UUID=18b29bfa-332a-409b-810c-5cc8a1dbb81e /boot ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-home /home ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-tmp /tmp ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-var /var ext4 defaults 0 2\n" "/dev/mapper/VolGroup00-swap_1 none swap sw 0 0\n" "/dev/sr0 /media/cdrom0 udf,iso9660 user,noauto 0 0\n") 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