Python: Can't create a binary file with a "with open(xxxxx)" line, using an os.path generated path (single backslash passed as double?)

I'm trying to download a video from vimeo (with this code https://github.com/moettle/hidden-vimeo-downloader, with some modified info for the request session info), and in the part of writing the file, I get an [Errno 22] message, as if the with open(PATH, "wb") read the backslashes as double backslashes

i.e: if PATH is something like "folder\filename.txt", the terminal's output shows OSError: [Errno 22] Invalid argument: 'folder\filename.txt'

This is my code:

    r = requests.get(current_segement_url)
    v_seg_file = os.path.join(out_video ,"video-" + segment_base_name + str(i) + segment_base_ext)

# Just to print out the actual variable's content
    print(v_seg_file)

    with open(v_seg_file, "wb") as f:
        f.write(r.content)

(i've separated the path to v_seg_file to see if the .encode() method or playing with replacements or raw strings could work, but it doesn't.)

The current output is:

segments_video_8cf150a5-2ce1-4adc-bb37-111111111111\video-segment-0.m4s?r=11111111dHJhbDE%3D
Traceback (most recent call last):
File "C:\Users\XXXXX\.......\hidden-vimeo-downloader\vimeo-downloader.py", line 78, in <module>
with open(v_seg_file, "wb") as f:
         ^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 22] Invalid argument: 'segments_video_8cf150a5-2ce1-4adc-bb37-111111111111\\video-segment-0.m4s?r=11111111dHJhbDE%3D'   

(the actual file path was modified here, but it's generated automatically by the code)

The question is: Why can't I create the file? Some lines above, the directory is created if it doesn't exist. I also tried writing in "wb", "wb+", "w+b" without success

I think the problem is that with open( here somehow transforms a single backslash into two? I mean, the printed output of v_seg_file is OK, which has been created with os.path.join (that should be OK)

I also tried another script to test this writing statements just as a double check, and it works fine for non-binary writing.

import os

out_video = "folder"
segment_base_name = "xxx"
segment_base_ext = "yyy"
i = 0

v_seg_file = os.path.join(out_video ,"video-" + segment_base_name + str(i) + segment_base_ext)

print(v_seg_file)

if not os.path.exists(out_video):
    os.makedirs(out_video)
    print("Directory created successfully!")
else:
    print("Directory already exists!")

with open(v_seg_file, "w") as f:
    f.write("file written")

(result: the file folder\video-xxx0yyy was created without issues, and consists of only one line of text "file written")

Could this be a platform issue with the BINARY writing? I'm running this code locally in a Windows machine, but yesterday i run it in Github codespaces (with another video URL) and worked fine.

Chances are, codespaces is running Linux, hence why the file creation worked there. Windows and *nix have different rules regarding what characters are allowed in a filename.

Please refer to this SO answer for more specifics.

As you’re on Windows, there are many disallowed characters, specifically for your case, a question mark. The file being binary vs plaintext, has no bearing here.

The fix:

You’ll need to clean the filename before attempting to create the file on Win.

Tip: The Python str.translate method is very useful for making multiple replacements in a string.