os.path.expanduser can be used to get a users home directory.

#!/usr/bin/python
import os

home = os.path.expanduser('~')
print(home)

Which should return something like this (on a Mac or Linux system).

/home/john.doe

If using Python version 3.4 or high, Path.home() can be used.

#!/usr/bin/python
from pathlib import Path

home = Path.home()
print(home)

Which should return something like this (on a Windows system).

C:\Users\johndoe

Often, Python scripts run on Windows need two backslashes such as C:\\Users\\johndoe. This is kind of weird, but I usually have to go with a single back slash following Path.home when using f format and then double back slashes for any additional directories.

f"{Path.home()}\Downloads\\"