UserString subtypes parameterless __init__

[Lordfirespeed]

Description

Subtypes of UserString cannot be initialized without a seq argument as the builtin str can.

Reproduction

from collections import UserString

class MyString(UserString):
    pass

>>> str()
''
>>> MyString()
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    MyString()
    ~~~~~~~~^^
TypeError: UserString.__init__() missing 1 required positional argument: 'seq'

Workaround

from collections import UserString

class MyString(UserString):
    def __init__(self, seq: object = str()) -> None:
        super().__init__(seq)

CPython versions tested on:

3.13

Operating systems tested on:

Linux

[brianschubert]

This is consistent with the docs, which indicate that the seq parameter is required (note the lack of surrounding brackets). So, not exactly a bug, but probably a reasonable feature request.

[picnixz]

cc @rhettinger: what was the rationale of having a required seq? was it an oversight or was it because an empty user-defined string should rather be instantiated using '' instead (namely, there is no real use-case for an empty UserString)