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gh-82665 Mention that HTMLParser.handle_starttag value can be None #134312

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gh-82665 Mention that HTMLParser.handle_starttag value can be None #134312

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Specify boolean attribute behavior in parser
Fearless-Badger May 20, 2025
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Merge branch 'main' of https://github.com/python/cpython
Fearless-Badger May 20, 2025
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13 changes: 12 additions & 1 deletion Doc/library/html.parser.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -134,7 +134,8 @@ implementations do nothing (except for :meth:`~HTMLParser.handle_startendtag`):
argument is a list of ``(name, value)`` pairs containing the attributes found
inside the tag's ``<>`` brackets. The *name* will be translated to lower case,
and quotes in the *value* have been removed, and character and entity references
have been replaced.
have been replaced. If a boolean attribute is encountered, the *value* for the
``(name, value)`` attribute pair will be ``None``.
Comment on lines +137 to +138
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@serhiy-storchaka serhiy-storchaka Nov 20, 2025

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Boolean attributes can also be written as disabled=disabled or even disabled="". When the value is absent, this is called empty attribute. This is syntax, not semantic.

Suggested change
have been replaced. If a boolean attribute is encountered, the *value* for the
``(name, value)`` attribute pair will be ``None``.
have been replaced. For empty attributes, *value* is ``None``.


For instance, for the tag ``<A HREF="https://www.cwi.nl/">``, this method
would be called as ``handle_starttag('a', [('href', 'https://www.cwi.nl/')])``.
Expand Down Expand Up @@ -310,6 +311,16 @@ further parsing:
Data : alert("<strong>hello!</strong>");
End tag : script

Boolean attributes have a *value* of ``None``:

.. doctest::

>>> parser.feed("<script src='/script.js' defer></script>")
Start tag: script
attr: ('src', '/script.js')
attr: ('defer', None)
End tag : script

Parsing comments:

.. doctest::
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