Anyone who is wondering how to get the image extension then you can try split method of string on image url:
str_arr = str(img_url).split('.')
img_ext = '.' + str_arr[3] #www.bigbasket.com/patanjali-atta.jpg (jpg is after 3rd dot so)
img_data = requests.get(img_url).content
with open(img_name + img_ext, 'wb') as handler:
handler.write(img_data)