First of all, you need to install the library:

$ pip3 install fints

Then, you can initialize a FinTS client by providing your bank's BLZ, your username and PIN as well as the HBCI endpoint of your bank. Logging in with a signature file or chip card is currently not supported. For example:

import logging
from datetime import date
import getpass
from fints.client import FinTS3PinTanClient

logging.basicConfig(level=logging.DEBUG)
f = FinTS3PinTanClient(
    '123456789',  # Your bank's BLZ
    'myusername',  # Your login name
    getpass.getpass('PIN:'),  # Your banking PIN
    'https://hbci-pintan.gad.de/cgi-bin/hbciservlet'
)

You can then execute commands using the client instance:

accounts = f.get_sepa_accounts()

Go on to the next pages to find out what commands are supported!