createCustomerCard.py

# use Square's SDK to make your job easier
import squareconnect
from squareconnect.apis.customers_api import CustomersApi
from squareconnect.models.create_customer_card_request import CreateCustomerCardRequest

# setup authorization with your access token
squareconnect.configuration.access_token = 'sandbox-sq0atb-XXXXXXXX'

# using a hardcoded nonce, but in a production evironment you'll need to use the
# payment form: 
# https://docs.connect.squareup.com/payments/sqpaymentform/sqpaymentform-overview
nonce = 'fake-card-nonce-ok'

# Your customer id will likely be dynimcally chosen, but again we will use a 
# hard coded example
customer_id = 'CBASEBW5Mh0hBis1BAGMoXamePwgAQ'

# create an instance of the Location API class
api_instance = CustomersApi()
customer_card = CreateCustomerCardRequest()
customer_card.card_nonce = nonce
customer_card.cardholder_name = 'Sam Smith'

# call the API to create the employee and print the results
api_response = api_instance.create_customer_card(customer_id,customer_card)
print (api_response)