Performing PCI compatibility alone is very difficult. Details are available here .
The most common payment pattern in App Engine is to use a payment gateway that is responsible for PCI compliance.
Typically, these services provide you with an authorization token to correlate with users, which you can use to create payments.
Popular Python Gateways
Here are some links to payment gateways to get you started.
- Braintree , I used this in the process of creating the application and it works great
- Stripe, , .