How does named group syntax differ from standard PCRE or JavaScript in Python?

Python uses (?P ...) for defining named capture groups and (?P=name) for backreferences, whereas other engines often use (? ...).

Can I use comments and multi-line formatting in my regex?

Yes, enabling the VERBOSE (x) flag allows you to add whitespace and # comments within your regular expression pattern.

How do I reference named capture groups in the replacement field?

Use Python's \g syntax or standard numbered references like \1 or \g in the replacement template input.

Are character classes like \d and \w matching Unicode characters by default?

Yes, standard string patterns in Python match Unicode by default; you can enable the ASCII (a) flag to restrict them to ASCII ranges.

Does this tool generate executable Python code?

Yes, it automatically generates ready-to-paste Python code snippets including the specified re flags and named group access calls.

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Python Regex Tester (re module)

Test Python re patterns online: (?P<name>…) named groups, (?P=name) backreferences, VERBOSE patterns, findall behavior, and \g<name> replace templates — plus ready-to-paste Python code.

Details

What this tool helps you do

A regex tester for Python\u0027s built-in re module. Write the pattern exactly as in Python — named groups (?P…), the named backreference (?P=tag), VERBOSE free-spacing with # comments, re.IGNORECASE / MULTILINE / DOTALL flags — and it is translated to the platform\u0027s ECMAScript engine and executed against your test string. You get every match (findall/finditer style with the g toggle), a capture-group table with names, and a re.sub-style replace preview where \1, \g<1> and \g templates are translated for the preview. Ready-to-paste Python code with the right re.* flags and match.group(\u0027name\u0027) access is generated. Python-specific semantics are honored: \d \w \s are Unicode by default for str patterns (uncheck to emulate re.ASCII), possessive quantifiers and atomic groups (Python 3.11+) are emulated with lookahead-capture, and .NET-style (?…) syntax is rejected with a hint to use (?P…) — exactly as Python would.

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Python Regex Tester (re module)

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Key facts

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Use cases

Examples

1. Rearranging Name Formats with re.sub

2. Matching Symmetrical XML/HTML Tags

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