I used pyodbc to connect my MSSQL server, using this code lines;
con = pyodbc.connect("DRIVER={SQL Server}; SERVER=my_server_ip; DATABASE=db_name; UID=user_id; PWD=password; CHARSET=UNICODE")
cur = con.cursor()
(First I wrote some more code to convert database tables into CSV files then uploaded them.)
Afterwards I used bulkloader to upload and download from tables. Bulkloader documentation is lack of examples tho. I wrote this code to upload and download via os library that provides dos commands to work in script. Provided CSV files to upload from the file I stored them after conversion.
Upload:
os.system("appcfg.py upload_data --config_file=bulkloader.yaml --log_file=/logs --url=http://my_app_name.appspot.com/_ah/remote_api --kind=kind --filename=CSV_files/table_name.csv --email=my_email_adress)
Download:
os.system("bulkloader.py --download --config_file=bulkloader.yaml --kind=kind --url=http://my_app_name.appspot.com/_ah/remote_api --filename=CSV_files/table_name.csv")