To upload a file from url to a cloud storage system, usually it is required to download that file on a server, and then upload it to the cloud storage.
For large files,
Yes, it's possible. You can generate an upload URL (using Cloud Storage API) and provide it to a client that should use it in a POST request.
Here is docs for PHP but this approach should be working for Python as well.
Here is an example: https://github.com/GoogleCloudPlatform/storage-signedurls-python