Google Play:

from pyinapp import GooglePlayValidator, InAppValidationError


bundle_id = 'com.yourcompany.yourapp'
api_key = 'API key from the developer console'
validator = GooglePlayValidator(bundle_id, api_key)

try:
    purchases = validator.validate('receipt', 'signature')
    process_purchases(purchases)
except InAppValidationError:
    """ handle validation error """

App Store:

from pyinapp import AppStoreValidator, InAppValidationError


bundle_id = 'com.yourcompany.yourapp'
validator = AppStoreValidator(bundle_id)

try:
    purchases = validator.validate('receipt')
    process_purchases(purchases)
except InAppValidationError:
    """ handle validation error """

Important! If your version is under 0.1.3, you need to check the type of purchases. For the sake of convenience you can process purchases this way:

def process_purchases(purchases):
    process(*purchases) if isinstance(purchases, list) else process(purchases)


def process(*purchases):
    for p in purchases:
        """ for instance, save p to db and add a player some coins for it """

This approach allows to process both Google Play and App Store purchases the same way.