Issue with Path.copy

Python Help
1

Hello everyone. I am new here and I am looking for help with an issue that I am having with copying files using pathlib. I’m running python3.14 on Linux Mint.

When I try to use the .copy method on pathlib’s Path class to copy a file, it raises an OSError[22]. So far it looks like this happens when trying to copy a non-empty file. Here is the script that I am using to reproduce the error.

#!/usr/bin/env python3

from pathlib import Path

SRC = Path(__file__).parent / 'test1.txt'
DEST = Path(__file__).parent / 'test2.txt'

SRC.copy(DEST)

The contents of the file test1.txt are below:

123456789
123456789
123456789
123456789
123456789
123456789
123456789
123456789
123456789
123456789
123456789

And here is the traceback that I get from running the code.

Traceback (most recent call last):
  File "/home/robert/src/Sandbox/Test/./copy.py", line 8, in <module>
    SRC.copy(DEST)
  File "/usr/lib/python3.14/pathlib/__init__.py", line 1103, in copy
    target._copy_from(self, **kwargs)
  File "/usr/lib/python3.14/pathlib/__init__.py", line 1134, in _copy_from
    self._copy_from_file(source, preserve_metadata)
  File "/usr/lib/python3.14/pathlib/__init__.py", line 1140, in _copy_from_file
    copyfileobj(source_f, target_f)
  File "/usr/lib/python3.14/pathlib/_os.py", line 160, in copyfileobj
    raise err
  File "/usr/lib/python3.14/pathlib/_os.py", line 148, in copyfileobj
    raise err
  File "/usr/lib/python3.14/pathlib/_os.py", line 144, in copyfileobj
    _copy_file_range(source_fd, target_fd)
  File "/usr/lib/python3.14/pathlib/_os.py", line 78, in _copy_file_range
    sent = os.copy_file_range(source_fd, target_fd, blocksize,
OSError: [Errno 22] Invalid argument: '/home/robert/src/Sandbox/Test/test1.txt' -> '/home/robert/src/Sandbox/Test/test2.txt'

It seems to work fine when I use shutil.copy2 instead. Does anyone know why this might be occurring?

Cheers,

-Robert

2

Also using Python 3.14 on Linux Mint, it works for me.

3

Hello,

I don’t believe that the pathlib library currently has a dedicated copy built in function for copying files. This is why you are getting the OSError: [Errno 22] Invalid argument.

If you are using an editor like PyCharm, it will autodetect the available functions and classes available to you once adding a “.” dot after the keyword, you’ll notice that the copy keyword does not appear.

Update:
I am using version: 3.13.0 - So this might have something to do with it.

4

It was added in Python 3.14.

5

@MRAB

Thanks. Yes, I just did a search and I came to this conclusion. Nice to know that the pathlib library is adding this functionality.

6

Your program runs fine for me on my copy of 3.14, so I don’t see anything in your source that seems suspicious.

Odd to me is that the os.copy_file_range() call seems to want a fd, but the error shows that it received paths instead.

When I set a breakpoint there on my copy (which works), it does appear to be passing fds…

(Pdb) b /usr/lib/python3.14/pathlib/_os.py:78
Breakpoint 1 at /usr/lib/python3.14/pathlib/_os.py:78
(Pdb) c
> /usr/lib/python3.14/pathlib/_os.py(78)_copy_file_range()
-> sent = os.copy_file_range(source_fd, target_fd, blocksize,
(Pdb) p source_fd, target_fd
(3, 4)

So not sure why that’s not working in your run…..

7

Interesting. If you don’t mind, would you let me know what minor version you’re on and how you installed your python? I got mine through the deadsnakes ppa: https://launchpad.net/~deadsnakes/+archive/ubuntu/ppa.

8

I’m on WSL2 / ubuntu and fired up a new UV environment and pinned python to 3.14. Looks like that got me 3.14.2

:/tmp/test/src$ uv run python -V
Python 3.14.2
9

Thanks for checking it out. That is interesting. I did notice that os.copy_file_range() seemed to be raising the exception. It certainly seems odd since it does look like its supposed to take fds.

10

And i’m not sure if the “→” is part of the argument or not. I wondered if a symlink might be getting misinterpreted somewhere and that arrow is part of it (or if it’s just the error showing source and dest). If the very last path is a symlink it had no problem. But I didn’t test if maybe another component could be doing something odd.

11

Looks like I’m on 3.14.2 as well. I’ll try installing from a source other than deadsnakes and see if the issue persists when I have a moment. Thank you again for giving this a look.

12

Reading the man page for copy_file_range(2), Ernno 22 = EINVAL can be producded in three cases:

       EINVAL The flags argument is not 0.

       EINVAL fd_in and fd_out refer to the same file and the source and
              target ranges overlap.

       EINVAL Either fd_in or fd_out is not a regular file.

Based on the message you are seeing (which AFAICT is the result of strerror, not anything python tried to guess), I think case 3 is the one that actually happened, so either of those two files is not a regular file. Is one of them a symlink or something like this? If you delete both of them and then recreate the src file, does this still happen?

13

I tried lots of things on my machine to regenerate the error, but “non-regular” files didn’t do it for me (generated other errors). Only thing that came close for me was either hard- or soft- linking the source and dest together. That got a similar error 22, but with slightly different text. (Could be due to me being on a different Linux distro).

OSError: [Errno 22] Source and target are the same file: '/tmp/test/src/test1.txt' -> '/tmp/test/src/test2.txt'

I wonder if this is the case for the OP, but the OS is giving a different error.