Download a private facebook video

facebook_downloader.py

#!/usr/bin/env python3

import json
import re
import requests
import sys

def slurp(p):
    with open(p, "r") as f:
        return f.read()

def download_file(url, local_filename):
    # NOTE the stream=True parameter below
    with requests.get(url, stream=True) as r:
        r.raise_for_status()
        with open(local_filename, 'wb') as f:
            for chunk in r.iter_content(chunk_size=8192): 
                f.write(chunk)
    
def do_the_job(html_source_file):
    html_source = slurp(html_source_file)
    scripts = re.findall(r'<script type="application/json"  data-content-len="\d+" data-sjs>(.+)</script>', html_source)
    for script in scripts:
        if "video\/mp4" not in script:
            continue
        parsed_script = json.loads(script)
        video_versions = parsed_script['require'][0][3][0]['__bbox']['require'][3][3][1]['__bbox']['result']['data']['video']['videoDeliveryResponseFragment']['videoDeliveryResponseResult']['progressive_urls']
        if ".mp4?" not in json.dumps(video_versions):
            raise Exception("no more")
        candidates = {}
        for video_version in video_versions:
            candidates[video_version['metadata']['quality']] = video_version['progressive_url']
        for quality in ["HD", "SD"]:
            url = candidates.get(quality)
            if not url:
                continue
            
            local_filename = html_source_file + ".mp4"
            print("Downloading", url, "to", local_filename)
            download_file(url, local_filename)
            break
            
        break

if __name__ == "__main__":
    do_the_job(*sys.argv[1:])