All standard library functions accepting str paths must accept PathLike as well

Inspired by gh-3484 that tried to fix this for wave.open() only but failed.

We need a centralized and universal approach instead so everything accepting str paths could automatically accept PathLike for free.

For this, we can amend stdlib functions to wrap their path arguments into pathlib.PurePath introduced in Python 3.4. Unlike os.fspath, it throws a nicely formatted exception for us:

os.fspath from the mentioned bpo-31412: wave.open takes a path-like object #3484:

cpython/Lib/aifc.py

Lines 912 to 918 in 4a82d65

    
           try: 
        
               f = os.fspath(f) 
        
           except TypeError: 
        
               if not hasattr(f, 'read') and not hasattr(f, 'write'): 
        
                   raise TypeError('open() takes str, a path-like object, ' 
        
                                   + 'or an open file-like object, ' 
        
                                   + f'not {type(f).__name__!r}') from None

PurePath:

>>> import pathlib
>>> pathlib.PurePath(16)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\Oleg\cpython\Lib\pathlib.py", line 267, in __new__
    return cls._from_parts(args)
           ^^^^^^^^^^^^^^^^^^^^^
  File "D:\Oleg\cpython\Lib\pathlib.py", line 316, in _from_parts
    drv, root, parts = self._parse_args(args)
                       ^^^^^^^^^^^^^^^^^^^^^^
  File "D:\Oleg\cpython\Lib\pathlib.py", line 300, in _parse_args
    a = os.fspath(a)
        ^^^^^^^^^^^^
TypeError: expected str, bytes or os.PathLike object, not int

It’s not clear to me what you’re proposing to change. Can you provide specifics?

How would PurePath(16)’s behavior change?

We need a centralized and universal approach instead so everything accepting str paths could automatically accept PathLike for free.

os.fspath is meant to do just that.

Note that importing pathlib and creating PurePath are relatively expensive operations (compared to os.fspath with strings). When the niceties they provide aren't useful, it's better to avoid them.

Unlike os.fspath, it throws a nicely formatted exception for us:

How can the error message from os.fspath be improved?

Unlike os.fspath, it throws a nicely formatted exception for us

I'm confused, pathlib.PurePath's error message in the thing you've posted is literally coming straight from os.fspath

Closing in favor of gh-103659.

Reopening after #103659 (comment):

BTW, I don't think #102425 applies here, the os.environ values are strings some of which happen to look like paths (or integers).

However, I'll return to this issue much later.

No need to reopen this for my comment on #103659 , I tried to say that this issue is not a reason for changing the behaviour of os.environ with PathLike objects.

The purpose of this issue is not clear. os.fspath() already has a clear error message. The caller can override it if it supports more types (for example, open file descriptors or open file objects). I do not see how using the pathlib.PurePath constructor can make this better. More, os.fspath() is more lightweight and faster than pathlib.PurePath().

@serhiy-storchaka

@serhiy-storchaka , "not planned" suits better, isn't it?

Navigation Menu

Repository navigation

All standard library functions accepting `str` paths must accept `PathLike` as well #102425

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

	try:
	f = os.fspath(f)
	except TypeError:
	if not hasattr(f, 'read') and not hasattr(f, 'write'):
	raise TypeError('open() takes str, a path-like object, '
	+ 'or an open file-like object, '
	+ f'not {type(f).__name__!r}') from None

All standard library functions accepting str paths must accept PathLike as well #102425

Description

Activity

ericvsmith commented on Mar 4, 2023

encukou commented on Mar 6, 2023

hauntsaninja commented on Mar 7, 2023

arhadthedev commented on Apr 21, 2023

arhadthedev commented on Apr 21, 2023

ronaldoussoren commented on Apr 21, 2023

serhiy-storchaka commented on Nov 3, 2025

efimov-mikhail commented on Nov 3, 2025

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions

All standard library functions accepting `str` paths must accept `PathLike` as well #102425