How do I check for a file to be finished downloading Python3?

Question

I am trying to figure out how to check if a download has been completed. Basically I want it to wait until the file is finished downloading then print: Download completed.

Here is my current code and what I am trying to do with it:

from  urllib import request

print("Are you sure you want to download the newest file? y/n")
answer = input()

while True:
    if answer == 'y':
        print("Downloading file...")
        downloading = True
        request.urlretrieve("FILE_URL", "FILE_NAME")
    elif answer == 'n':
         exit()
    else:
         print("That is not a valid answer, please answer with y/n.")
         answer = input()

#I need some sort of function here that checks if the file is still being 
#downloaded

when downloading == False:
    print("Download Completed.")

Answer 1

When urlretrieve returns, the file has already finished downloading.

See the usage example from the docs :

>>> import urllib.request
>>> local_filename, headers = urllib.request.urlretrieve('http://python.org/')
>>> html = open(local_filename)

As can be seen, the file is opened immediately after the call to urlretrieve , as it was already created and the content was already written there.

Answer 2

If you use the urllib.request.urlretrieve reporthook option, you can monitor the progress of the download, especially useful with large files, like so:

import urllib.request

def Download_Progress(block_num, block_size, total_size):
    downloaded = block_num * block_size
    progress = int((downloaded/total_size)*100)
    print ("Download Progress",str(progress),"%")

url = "https://somesite/some.pdf"
urllib.request.urlretrieve(url, 'mycopy.pdf', reporthook=Download_Progress)
print ("Finished")

You can achieve something similar with the requests package as well.

import requests
url = "https://somesite/some.pdf"

#Get the headers of the remote file
h = requests.head(url, allow_redirects=True)

#Get the size of the file
total_size = int(h.headers.get('content-length'))

#Request the file download with stream set to True
r = requests.get(url, stream=True)

#Open a local file for writing
localfile = open("mycopy.pdf", "wb")
chunks = 0

#Process the file as it arrives
for chunk in r.iter_content(chunk_size=512):
    if chunk:
        chunks += 1
        downloaded = chunks * 512
        # An approximation as the chunks don't have to be 512 bytes
        progress = int((downloaded/total_size)*100)
        print ("Download Progress",str(progress),"%")
        localfile.write(chunk)
print("Finished")