BeautifulSoup

1. To check if an object is of NavigableString instance, one can use
   isinstance(your_obj, bs4.element.NavigableString)
2. file method executed as a member function of a tag object fails. https://en.wikipedia.org/wiki/Duck_typing
3. To download image from its url:
   import shutil; import requests
   url = 'http://example.com/img.png'
   response = requests.get(url, stream=True)
   with open('img.png', 'wb') as out_file:
       shutil.copyfileobj(response.raw, out_file)
   del response
   https://stackoverflow.com/questions/13137817/how-to-download-image-using-requests