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Cheddar Python Bindings

Project description

Cheddar Bindings for Python

A Python wrapper for Cheddar's application interface. Cheddar is a payment gateway for processing and executing transactions within a neat and universal API.

At the moment, the following payment methods and services are supported by Cheddar and this library:

  • CardPay with optional addition for ComfortPay service – Tatra banka, a.s.
  • TatraPay – Tatra banka, a.s.
  • ePlatby VÚB – VÚB, a.s.
  • VÚB eCard – VÚB, a.s.
  • SporoPay – Slovenská sporiteľna, a.s.
  • iTerminal – Poštová banka, a.s.
  • GP webpay – Global Payments Europe, s.r.o.
  • PayPal – PayPal (Europe) S.à r.l. et Cie, S.C.A.

To see what is new or changed in the current version, check out the changelog.

Setup

You can install this package by using pip:

pip install cheddarpayments

If you fancy pipenv use:

pipenv install cheddarpayments

To install from source, run:

python setup.py install

For the API client to work you would need Python 2.7+ or Python 3.4+.

Usage

First off, you need to require the library and provide authentication information by providing your user handle and shared secret you got from the provider.

import cheddar

client = cheddar.Cheddar(
    cheddar.Configuration(
        cheddar.Environment.Production,
        "TEST",
        "00000000000000000000000000000000",
    )
)

In case you'd like to use the sandbox mode use cheddar.Environment.Sandbox when creating configuration object. You can also create your own environment pointing to any valid URL with Cheddar instance running:

my_test_environment = cheddar.Environment("test", "https://my.cheddar.test")

Please note that only VÚB eCard, iTerminal, GP webpay and PayPal currently allow for using their test environments so in case of other providers production URLs will be used! When using sandbox with supported bank or financial institution never use real world credit cards / accounts for testing payment methods implementation (they will not work). Always use virtual testing cards / accounts provided for this purpose by the payment institution.

Creating a transaction

It is quite simple to instantiate a payment.

Here’s a quick piece of example code to get you started which will call the Cheddar service and retrieve UUID – universal identifier of the transaction and set the transaction status to none (see next section for more on transaction statuses).

payment = client.payments.create(
    cheddar.Service.CARDPAY,
    {
        "amount": Decimal('9.99'),
        "currency": cheddar.Currency.EUR,
        "variable_symbol": "1000000000",
        "description": "My first test payment",
        "payer_name": "John Doe",
        "payer_email": "john@doe.com",
        "return_url": "https://my-test-server.dev",
        "notification_url": "https://my-test-server.dev",
    },
)

When using the wrapper in web context, the user's IP is automatically added to the data array from the environment variables. If you wish to provide your own, add payer_ip_address key with valid address as a value.

First argument is a service provider, which can currently be one of the following:

Service name Description
cheddar.Service.SPOROPAY SporoPay, Slovenská sporiteľňa
cheddar.Service.TATRAPAY TatraPay, Tatra banka
cheddar.Service.CARDPAY Cardpay, Tatra banka
cheddar.Service.EPLATBY ePlatby, VÚB
cheddar.Service.ECARD eCard, VÚB
cheddar.Service.PAYPAL PayPal Payments Standard, PayPal
cheddar.Service.GPWEBPAY GP webpay, Global Payments Europe
cheddar.Service.ITERMINAL iTerminal, Poštová banka

Second argument to the function call is an associative array of configuration options. Which options have to be used and which have no effect at all depends on the service provider. The next table lists all possible attributes:

Attribute name Data type Required? Notes
amount float amount required in the specified currency
currency string currency code as in ISO 4217
variable_symbol string
constant_symbol string
card_id string optional card token in periodical payments
applicable only to ComfortPay transactions
payer_name string customer’s name
payer_email string customer’s email (which has to be a valid e-mail address)
language string customer’s language
description string reference for the customer
reurn_url or callback string URL to return to after the payment
iTerminal does not use this attribute since you have to set this up once for all transactions in their administration interface
notification_url string URL to send notifications to
required for PayPal transactions
cpp_logo_image string header image at PayPal
applicable only to PayPal transactions
cpp_cart_border_color string HEX code of colour at PayPal
applicable only to PayPal transactions
periodicity integer periodicity in days, when the next periodical payment will be automatically executed; default value is 30 days
applicable only to ComfortPay transactions

Note that all of the supported currencies are available as a simple constant on cheddar.Currency class to make it easier in code.

After the call you can inspect the returning Payment object, which is described in the Getting transaction details part of this document.

To get to the URL of a payments gateway at the bank where the payment is processed just redirect the user to value of payment.redirect_url property.

After the payment process at the payment gateway is finished, you will be redirected to the URL you specified in return_url / callback parameter during the create call in the example above. The URL will have two more GET parameters added - uuid, for the payment identifier and status, for the current status of the payment transaction (for some payment methods this may change in time, and you will be notified about the change to the URL you specified in the notification_url parameter [see the Asynchronous transaction notifications part of this document for more info])

Allowed transaction statuses

Status name Description
none transaction has been created, but the user has not been redirected to bank’s payment gateway
in_progress user has been redirected to bank’s payment gateway
completed transaction has been successfully completed
denied or rejected transaction has been rejected by the bank (the most usual reasons include user error in inputting card details and insufficient funds)
timeout special temporary status used only by Tatra banka’s TatraPay service
pending special status for PayPal before an IPN notification has resolved the transaction status as either rejected or completed
cancelled in case of periodical payments available only with Tatra banka’s ComfortPay service this status means that planned transaction has been cancelled
expired old payment without clear result (e.g. user abandoned the payment form while at bank’s gateway)

Getting transaction details

To get all details of an existing payment transaction simply pass the UUID of the payment to the following method:

payment = client.payments.details(uuid)

Afterwards you can inspect the returning object, which contains these properties:

Property name Data type Always present? Default value Notes
uuid string
status string none current transaction status (see the next table)
variable_symbol string the same as was sent while creating the payment object (see previous section)
constant_symbol string 0308 payment for services
amount float 0.00 original amount of the transaction
refunded_amount float 0.00 refunded amount of the transaction
service_fee_amount float 0.00 provision for the transaction in card payments available when using CardPay / ComfortPay and set up with PGP encrypted statements or PayPal service
currency Currencies EUR currency of the transaction
periodicity integer 0 number of days in which next payment will be executed
periodicity_no integer 1 number of transaction in order (using the same variable symbol)
charge_on Datetime when was or should be this transaction executed
card_expire_on Datetime null date of card expiration available only when using ComfortPay or VÚB eCard service
card_no string masked card number available only when using ComfortPay or VÚB eCard service
transaction_identifier string internal transaction identifier of the bank available only when using CardPay / ComfortPay, TatraPay or VÚB eCard service

Asynchronous transaction notifications

Transactions may have a notification_url attribute (in case of PayPal and ComfortPay the attribute is mandatory), that will receive a ping on every change to a transaction (in case of PayPal or ComfortPay it is also the only way to find out the status of the payment).

Cheddar calls the value of notification_url attribute as POST request with GET attributes uuid and signature (which needs to be verified) and application/json body with full payment details as explained in the previous section.

To validate the signature, you need to call the following:

is_valid = client.messages.validate(uuid, signature);

In case the signature is incorrect a cheddar.errors.MessageIntegrityError is thrown, otherwise the function returns true. After a successful validation you can trust the json-encoded body of the request.

The JSON-encoded body will look something like this:

{
    "uuid": "b1fcc76a-d284-4cbc-bce9-b415dc973763",
    "service": {
        "handle": "cardpay",
        "provider": "Tatra banka, a.s.",
        "name": "CardPay"
    },
    "status": {
        "status": "completed",
        "description": "The payment has been approved by the bank or financial institution"
    },
    "variable_symbol": "1000000000",
    "constant_symbol": "0308",
    "amount": 9.99,
    "refunded_amount": 0,
    "service_fee_amount": 0,
    "currency": {
        "alpha_code": "EUR",
        "numeric_code": 978,
        "name": "Euro"
    },
    "periodicity": 0,
    "periodicity_no": 1,
    "created_at": "2018-12-01 10:34:26",
    "events": [],
    "note": "my first test payment",
    "card_no": "****************",
    "transaction_identifier": "Aq83Lys6WHdiP8TFo6pnkRvTlpC="
}

Updating planned transaction

The next use case is the ability to change date and / or amount of a next planned periodical playment. The output of the call is summary of the planned payment including its UUID.

import datetime

payment = client.payments.update(uuid, [
    "charge_on": datetime.date.today() + datetime.timedelta(days=1),
    "amount": Decimal('11.99')
]);

However, also the status of the planned payment might be changed – from none to cancelled or the other way. Just make sure that the charge_on attribute is set to correct value or explicitly set it, when changing the status.

Refunding transactions

With Poštová banka’s iTerminal service you might once request a refund on executed transaction in part, or in full. In case of Tatra banka's CardPay service you might request as many refunds as you'd like until sum of all prior refunds reaches the amount of the original transaction.

The reason is more informative and should be one of either requested_by_customer, fraudelent, duplicate or unknown (default). Currency has to be the same as when executing the original payment.

payment = client.payments.refund(uuid, [
    "amount": Decimal("11.99"),
    "currency": client.Currency.EUR,
    "reason": "requested_by_customer"
]);

Contributing

  1. Check for open issues or open a new issue for a feature request or a bug.
  2. Fork the repository and make your changes to the master branch (or branch off of it).
  3. Send a pull request.

Development

Run all tests on all supported Python versions:

make test

Run the linter with:

make lint

The client library uses Black for code formatting. Code must be formatted with Black before PRs are submitted. Run the formatter with:

make fmt

© 2019 BACKBONE, s.r.o.

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