Bug report

Checklist

• I am confident this is a bug in CPython, not a bug in a third-party project
• I have searched the CPython issue tracker, and am confident this bug has not been reported before

A clear and concise description of the bug

When trying to parse an INI with an indented key that follows a no-value key, an AttributeError is raised

importconfigparserlines= ['[SECT]\n','KEY1\n',' KEY2 = VAL2\n',# note the Space before the key!]conf=configparser.ConfigParser(comment_prefixes="",allow_no_value=True,strict=False,delimiters=('=', ),interpolation=None,)conf.read_file(lines,"test" )print(conf.__dict__['_sections' ] )

File "C:\Python311\Lib\configparser.py", line 1076, in _read          cursect[optname].append(value)    ^^^^^^^^^^^^^^^^^^^^^^^AttributeError: 'NoneType' object has no attribute 'append'

The reason is that ConfigParser assumes the second key is a continuation line and therefore further assumes thatcursect[optname] is initialized in the following check:

if (cursectisnotNoneandoptnameandcur_indent_level>indent_level):cursect[optname].append(value)

Suggested fix: add a check forcursect[optname] is not None:

if (cursectisnotNoneandoptnameandcursect[optname]isnotNoneandcur_indent_level>indent_level):cursect[optname].append(value)

With this check added, the print will output:

{'SECT': {'key1':None,'key2':'VAL2'}}

If the suggested fix is not acceptable, please consider to add a check and maybe raise aParsingError, but making an assumption aboutcursect[optname] and let it raise an AttributeError is just not a good thing, IMHO.

Your environment

• CPython versions tested on: 3.7, 3.9, 3.11.2 (Python 3.11.2 (tags/v3.11.2:878ead1, Feb 7 2023, 16:38:35) [MSC v.1934 64 bit (AMD64)] on win32)
• Operating system and architecture: Windows 10 Pro, 64 bit

Linked PRs

• gh-107625: configparser: Raise ParsingError if a key contains empty value #107651