ConfigParser replaces unnamed section on every read call

[PalmtopTiger]

Bug report

Bug description:

from configparser import ConfigParser

config = ConfigParser(allow_unnamed_section=True)
config.read(['first.ini', 'second.ini'])

# now the unnamed section contains values ​​only from the second file:
print(config._sections)
# {
# <UNNAMED_SECTION>: {'second_unnamed_option1': '1', 'second_unnamed_option2': '2'},
# 'first_section': {'first_section_option1': '1', 'first_section_option2': '2'},
# 'second_section': {'second_section_option1': '1', 'second_section_option2': '2'}
# }

I think the problem is somewhere here. The unnamed section is recreated on every call.
first.ini.txt
second.ini.txt

CPython versions tested on:

3.13

Operating systems tested on:

Windows

Linked PRs

• gh-127096: Do not recreate unnamed section on every read in ConfigParser #127228

[sobolevn]

Please, provide the contents of first.ini and second.ini, so it would be easier to reproduce the issue.

[PalmtopTiger]

Done

[ggggjlgl]

Due to network issues, I am unable to clone the cpython repository. The following are for reference:
file: configparser.py
class: class RawConfigParser(MutableMapping)
method: def _handle_rest(self, st, line, fpname)
modify to:

    def _handle_rest(self, st, line, fpname):
        # a section header or option header?
        if self._allow_unnamed_section and st.cursect is None:
            st.sectname = UNNAMED_SECTION
            if self._sections.get(st.sectname) is None:
                st.cursect = self._dict()
                self._sections[st.sectname] = st.cursect
            else:
                st.cursect = self._sections[st.sectname]
            self._proxies[st.sectname] = SectionProxy(self, st.sectname)
            st.elements_added.add(st.sectname)
            ...  # Omit subsequent code

[Agent-Hellboy]

Due to network issues, I am unable to clone the cpython repository. The following are for reference:

I am working on adding something in configparser, I can take a look and add a PR if you want.

[PalmtopTiger]

I created the PR myself. Thanks to everyone for your help!

[ggggjlgl]

Due to network issues, I am unable to clone the cpython repository. The following are for reference:

I am working on adding something in configparser, I can take a look and add a PR if you want.

Thank you. PalmtopTiger created the PR.