Re: File system path annotations

[Thomas Passin via Python-list]

On 6/19/2023 10:04 AM, Roel Schroeven via Python-list wrote:

Op 19/06/2023 om 11:44 schreef Peter Slížik:

Thank you, Roel. You've answered all my questions.

> [PEP 519]: ...as that can be represented with typing.Union[str, 
bytes, os.PathLike] easily enough and the hope is users

> will slowly gravitate to path objects only.

I read a lot on Python and, frankly, I don't see this happening. 
People on the Internet keep using /str/ as their path representation 
choice. Presumably, programmers don't feel the need to bother with a 
complex solution if the simplest option works just fine.
I agree, I don't see that happening either. I often find myself using 
str for paths: often simple filenames are all that's needed, and then I 
don't see much point in importing pathlib and wrapping the filenames in 
Path() constructors. I do tend to switch to path objects when I start 
needing to do operations on the paths, though.



If you are writing code that will run on both Windows and Linux/Mac, 
pathlib objects are very useful since the path separators will come out 
right with no extra effort. Also, the syntax for composing a path seems 
very natural (e.g., Path('a') / 'b' / 'c'), so that's a bonus.


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Re: File system path annotations

[Roel Schroeven via Python-list]

Op 19/06/2023 om 11:44 schreef Peter Slížik:

Thank you, Roel. You've answered all my questions.

> [PEP 519]: ...as that can be represented with typing.Union[str, 
bytes, os.PathLike] easily enough and the hope is users

> will slowly gravitate to path objects only.

I read a lot on Python and, frankly, I don't see this happening. 
People on the Internet keep using /str/ as their path representation 
choice. Presumably, programmers don't feel the need to bother with a 
complex solution if the simplest option works just fine.
I agree, I don't see that happening either. I often find myself using 
str for paths: often simple filenames are all that's needed, and then I 
don't see much point in importing pathlib and wrapping the filenames in 
Path() constructors. I do tend to switch to path objects when I start 
needing to do operations on the paths, though.


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stop to think if they should"
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Re: File system path annotations

[Peter Slížik via Python-list]

Thank you, Roel. You've answered all my questions.

> [PEP 519]: ...as that can be represented with typing.Union[str, bytes,
os.PathLike] easily enough and the hope is users
> will slowly gravitate to path objects only.

I read a lot on Python and, frankly, I don't see this happening. People on
the Internet keep using *str* as their path representation choice.
Presumably, programmers don't feel the need to bother with a complex
solution if the simplest option works just fine.

Peter
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Re: File system path annotations

[Roel Schroeven via Python-list]

Op 19/06/2023 om 10:43 schreef Peter Slížik via Python-list:

Hello,

what is the preferred way of annotating file system paths?

This StackOverflow answer 
(and a few others) recommend using the

str | os.PathLike

union.

However, byte arrays can be used as paths too, and including them
would make the annotation quite long.

You don't have to type out the whole thing every time. Define it somewhere:

PathLike = str | bytes | os.PathLike

and then you can use PathLike everywhere.

I also believe that str confirms to the PathLike definition. Please,
correct me if I'm wrong.
I don't think so: os.PathLike instances must have a __fspath__() method, 
which str and bytes don't have.

And finally - using paths in Python programs is so common, that one
would expect to have a special type (or type alias) in typing. Am I
missing something?
I agree there should be something like that. This StackOverflow answer 
(https://stackoverflow.com/a/68027757/59122) talks about something like 
that: _typeshed.AnyPath. It is used in the standard library, but 
apparently it doesn't exist at runtime and you need a trick to make it 
work. I would expect something better to exist, but as far as I can find 
out there isn't.


PEP 519 has a little section on the topic 
(https://peps.python.org/pep-0519/#provide-specific-type-hinting-support):


> Provide specific type hinting support
>
> There was some consideration to providing a generic typing.PathLike 
class which would allow for e.g. typing.PathLike[str] to specify a type 
hint for a path object which returned a string representation.
> While potentially beneficial, the usefulness was deemed too small to 
bother adding the type hint class.

>
> This also removed any desire to have a class in the typing module 
which represented the union of all acceptable path-representing types as 
that can be represented with typing.Union[str, bytes,
> os.PathLike] easily enough and the hope is users will slowly 
gravitate to path objects only.


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File system path annotations

[Peter Slížik via Python-list]

Hello,

what is the preferred way of annotating file system paths?

This StackOverflow answer 
(and a few others) recommend using the

str | os.PathLike

union.

However, byte arrays can be used as paths too, and including them
would make the annotation quite long.

I also believe that str confirms to the PathLike definition. Please,
correct me if I'm wrong.

And finally - using paths in Python programs is so common, that one
would expect to have a special type (or type alias) in typing. Am I
missing something?

My apologies if I'm asking the obvious, but after some googling I came
to the conclusion that information on this topic is surprisingly
limited to a few StackOverflow questions.

Best regards,

Peter
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