Windows has a concept of current directory for each drive. Because of that, "c:sourcedir" means "sourcedir" inside the current C: directory, and you'll need to specify an absolute directory.

Any of these should work and give the same result, but I don't have a Windows VM fired up at the moment to double check:

"c:/sourcedir"
os.path.join("/", "c:", "sourcedir")
os.path.join("c:/", "sourcedir")

os.path is string-based while pathlib is object oriented

os.path operates on strings while pathlib is object-oriented (the documentation at this link speaks about Object-oriented filesystem paths). So if "/home/test/test.txt" is the absolute path (in POSIX format) to access to the file test.txt in the directory /home/test/, the instructions:

from os import path

path_1 = path.join("/home", "test", "test.txt")

(executed in a Linux system) return in path_1, the string "/home/test/test.txt" (link to os.path.join() documentation.)

On the other hand, the following commands:

from pathlib import Path

path_2 = Path("/home") / "test" / "test.txt"

return an object called path_2 which represents the file.

A function and a method available with the 2 approaches

By the previous initialization, essentially:

• The string path_1 can be used as argument of other functions of the module os.path. For example, to check if a file exists:

  from os import path
  
  if path.exists(path_1):
      # the file exists
      do stuff
  

• The object path_2 is an instance of the class pathlib.Path, so with this object it is possible to call all methods of the class Path.

  Furthermore, if path_2 is created on a POSIX compliant system (such as Linux), its type is PosixPath (a subclass of Path), else if path_2 is created on a Windows system, its type is WindowsPath (a subclass of the class Path).

  An example of the methods available on the object path_2 is the exists() method. The snippet of code below shows how it is used:

  from pathlib import Path
  
  if path_2.exists():
      # the file exists
      do stuff
  

Link

See this article to learn about other differences between the two ways of managing paths with Python: Paths in Python: Comparing os.path and pathlib modules

You could use the f-string in python (see documentation).

In your case:

request_path  = f"{BASE_DIR}/{filepath}"

Be aware that you need an extra slash "/" between your file location variables (BASE_DIR and filepath) to complete the full file location properly.

Hope this helps!

consider to use os.path.abspath this will evaluate the absolute path

or One can use os.path.normpath this will return the normalized path (Normalize path, eliminating double slashes, etc.)

One should pick one of these functions depending on requirements

In the case of abspath In Your example, You don't need to use os.path.join

os.path.abspath("../../my_dir")

os.path.normpath should be used if you are interested in the relative path.

>>> os.path.normpath("../my_dir/../my_dir")
'../my_dir'

Other references for handling with file paths:

• pathlib - Object-oriented filesystem paths
• os.path— Common pathname manipulations