How can I get size of file while downloading it in Python

You can get the file size from the header

import requests
r = requests.get(download_link)
headers = r.headers
file_size = headers.get('Content-Length')

I found what i was looking for: ref: https://requests.readthedocs.io/en/master/user/advanced/#body-content-workflow

with requests.get(url, stream=True) as r:
   downloaded=0
   total =  int(r.headers['content-length'])
   for i in r.iter_content():
       downloaded+=len(i)
       print(downloaded)

I too was looking for a solution and found one. Use requests with stream=True and tqdm.

To install tqdm with python3, use:

python3 -m pip install tqdm

Code to download a video from MITOpenCourseWare:

import requests
from tqdm import tqdm

link = 'http://www.archive.org/download/MIT6.006F11/MIT6_006F11_lec01_300k.mp4'
filename = 'video.mp4'
response = requests.get(link, stream=True)
if response.status_code == requests.codes.ok:
    total_size = int(response.headers.get('Content-Length', 0))
    downloaded_size = 0
    print(f'contentLength: {total_size} MB')
    with open(filename, 'wb') as handle,\
        tqdm(unit='B', total=total_size, desc=filename, unit_scale=True, unit_divisor=1024) as bar:
        for chunk in response.iter_content(chunk_size=1024*1024):
            size = handle.write(chunk)
            bar.update(size)
            downloaded_size += size

The variable downloaded_size for each loop gives the current downloaded size and total_size gives the total size.

Assumptions:

1. The website responds with a Content-Length