See Authentication for the default behavior of the DataSourceClient.
from domino.data_sources import DataSourceClient
custom_token_file = "/valid/token/file/location"
client = DataSourceClient(token_file=custom_token_file)
db = client.get_datasource("my-db")
library(DominoDataR)
client <- DominoDataR::datasource_client(token_file = "/valid/token/file/location")