python selenium, find out when a download has completed?

I came across this problem recently. I was downloading multiple files at once and had to build in a way to timeout if the downloads failed.

The code checks the filenames in some download directory every second and exits once they are complete or if it takes longer than 20 seconds to finish. The returned download time was used to check if the downloads were successful or if it timed out.

import time
import os

def download_wait(path_to_downloads):
    seconds = 0
    dl_wait = True
    while dl_wait and seconds < 20:
        time.sleep(1)
        dl_wait = False
        for fname in os.listdir(path_to_downloads):
            if fname.endswith('.crdownload'):
                dl_wait = True
        seconds += 1
    return seconds

I believe that this only works with chrome files as they end with the .crdownload extension. There may be a similar way to check in other browsers.

Edit: I recently changed the way that I use this function for times that .crdownload does not appear as the extension. Essentially this just waits for the correct number of files as well.

def download_wait(directory, timeout, nfiles=None):
    """
    Wait for downloads to finish with a specified timeout.

    Args
    ----
    directory : str
        The path to the folder where the files will be downloaded.
    timeout : int
        How many seconds to wait until timing out.
    nfiles : int, defaults to None
        If provided, also wait for the expected number of files.

    """
    seconds = 0
    dl_wait = True
    while dl_wait and seconds < timeout:
        time.sleep(1)
        dl_wait = False
        files = os.listdir(directory)
        if nfiles and len(files) != nfiles:
            dl_wait = True

        for fname in files:
            if fname.endswith('.crdownload'):
                dl_wait = True

        seconds += 1
    return seconds