I was surprised by the following behavior: class MyStr(str): def __getitem__(self, key): if isinstance(key, slice) and key.start is key.stop is key.end: return self return type(self)(super().__getitem__(key)) my_foo = MyStr("foo") MY_FOO = MyStr("FOO") My_Foo = MyStr("Foo") empty = MyStr("") assert type(my_foo.casefold()) is str assert type(MY_FOO.capitalize()) is str assert type(my_foo.center(3)) is str assert type(my_foo.expandtabs()) is str assert type(my_foo.join(())) is str assert type(my_foo.ljust(3)) is str assert type(my_foo.lower()) is str assert type(my_foo.lstrip()) is str assert type(my_foo.replace("x", "y")) is str assert type(my_foo.split()[0]) is str assert type(my_foo.splitlines()[0]) is str assert type(my_foo.strip()) is str assert type(empty.swapcase()) is str assert type(My_Foo.title()) is str assert type(MY_FOO.upper()) is str assert type(my_foo.zfill(3)) is str assert type(my_foo.partition("z")[0]) is MyStr assert type(my_foo.format()) is MyStr I was under the impression that all of the ``str`` methods exclusively returned base ``str`` objects. Is there any reason why those two are different, and is there a reason that would apply to ``removeprefix`` and ``removesuffix`` as well?