title: How to get the aws s3 object key using django-storages and boto3
body: <p>I am using django-storage and boto3 for media and static files using aws s3. I need to get the object key of aws s3 bucket, so that I can generate a url for that object.</p>
  
  <pre><code>client = boto3.client('s3')
  bucket_name = 'django-bucket'
  
  key = ???
  
  u = client.generate_presigned_url('get_object', Params = {'Bucket': bucket_name, 'Key': key,'ResponseContentType':'image/jpeg', 'ResponseContentDisposition': 'attachment; filename="your-filename.jpeg"'}, ExpiresIn = 1000)
  </code></pre>
  
  <p>These are in my settings:</p>
  
  <pre><code>STATICFILES_LOCATION = 'static'
  MEDIAFILES_LOCATION = 'media'
  STATICFILES_STORAGE = 'myproject.custom_storages.StaticStorage'
  DEFAULT_FILE_STORAGE = 'myproject.custom_storages.MediaStorage'
  AWS_ACCESS_KEY_ID = "my_access_key_id"
  AWS_SECRET_ACCESS_KEY = "my_secret_access_key"
  AWS_STORAGE_BUCKET_NAME = "django-bucket"
  AWS_QUERYSTRING_AUTH = False
  AWS_S3_CUSTOM_DOMAIN = AWS_STORAGE_BUCKET_NAME + ".s3.amazonaws.com"
  # static media settings
  STATIC_URL = "https://" + AWS_STORAGE_BUCKET_NAME + ".s3.amazonaws.com/"
  MEDIA_URL = STATIC_URL + "media/"
  ADMIN_MEDIA_PREFIX = STATIC_URL + "admin/"
  </code></pre>
  
  <p>I can get the file path of the image file</p>
  
  <pre><code>ui = UserImage.objects.get(user=user_id, image=image_id)
  url = ui.image.url
  
  'https://django-bucket.s3.amazonaws.com/media/user_image/1497598249_49.jpeg'
  </code></pre>
  
  <p>But I don't know how to get the s3 object key so that I can generate a url for that object.</p>