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
Processing...

Test String

Code Generator

Language

Generated Code

import re regex = re.compile(r"(?<!&)(?:\b(?:nbsp|quot|divide)|#[0-9a-f]+);", flags=re.MULTILINE | re.IGNORECASE) test_str = ("I have a huge HTML with several special chars, in the forms &nbsp; or \"&#82173333;.\n" "Faulty HEX: #82173333;\n" "Some of them are wrong, because they lack the initial &.\n\n" "I would like to search for such wrong spacial chars. I know that I can search all the right special chars by means of the following regex:\n\n" " \\&(?:[a-z]+|#x?\\d+);\\\n" "But I'd need a regex useful to search the wrong ones (without the initial &). Can you help me? Thanks in advance\n\n" "Edit:\n\n" "As suggested, I post an example. My HTML cointains the following statement:\n\n" " <![CDATA[<nolink>blablabla&nbsp;blablabla</nolink>]]>nbsp;\n" "where we have 2 special HTML character:\n" "divide;\n" "&divide;\n" "&nbsp;\n" "quot;\n" "I'm interested in finding the second item, because it is wrong (laking the initial &).\n\n" "So the output of the requested regex should be: quot;") 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