Why does this unpredictable behavior occur with the configparser module?

Question

Python

Why

config = ConfigParser()
config.read(self._config_path)

Not equal

second_config = ConfigParser().read(self._config_path)

?

dir from the first example

['BOOLEAN_STATES', 'NONSPACECRE', 'OPTCRE', 'OPTCRE_NV', 'SECTCRE', '_DEFAULT_INTERPOLATION', '_MutableMapping__marker', '_OPT_NV_TMPL', '_OPT_TMPL', '_SECT_TMPL', '__abstractmethods__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__setattr__', '__setitem__', '__sizeof__', '__slots__', '__str__', '__subclasshook__', '__weakref__', '_abc_impl', '_allow_no_value', '_comment_prefixes', '_convert_to_boolean', '_converters', '_defaults', '_delimiters', '_dict', '_empty_lines_in_values', '_get', '_get_conv', '_handle_error', '_inline_comment_prefixes', '_interpolation', '_join_multiline_values', '_optcre', '_proxies', '_read', '_read_defaults', '_sections', '_strict', '_unify_values', '_validate_value_types', '_write_section', 'add_section', 'clear', 'converters', 'default_section', 'defaults', 'get', 'getboolean', 'getfloat', 'getint', 'has_option', 'has_section', 'items', 'keys', 'options', 'optionxform', 'pop', 'popitem', 'read', 'read_dict', 'read_file', 'read_string', 'readfp', 'remove_option', 'remove_section', 'sections', 'set', 'setdefault', 'update', 'values', 'write']

dir from the second example

['BOOLEAN_STATES', 'NONSPACECRE', 'OPTCRE', 'OPTCRE_NV', 'SECTCRE', ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

Accordingly, when
assert config == second_config
an exception is raised

Answer 1

Because in the first case, the read method is simply called, and in the second, besides this, the config variable is also assigned the result of calling the read method