Common Square API Patterns

Learn how the Square Python SDK supports the common Square API features.

Some of the Square API patterns are used across various APIs. These include the following:

• Pagination - Many Square API operations limit the size of the response. When the result of the API operation exceeds the limit, the API truncates the result. You must make a series of requests to retrieve all the data. This is referred to as pagination.
• Idempotency key - Most Square APIs that perform create, update, or delete operations require idempotency keys to protect against making duplicate calls that can have negative consequences (for example, charging a card on file twice).
• Object versioning - Some Square resources (for example, the Customer object) have versions assigned. The version numbers enable optimistic concurrency, which is the ability for multiple transactions to complete without interfering with each other.
• Clear API object fields - Square API update endpoints that support sparse updates allow you to clear fields by setting the value to None. Note that update_order requires an X-Clear-Null: true HTTP header to indicate that the request contains a None field update.

These Square API patterns are exposed in the Square Python SDK.

Square API pagination support lets you split a full query result set into pages that are retrieved over a sequence of requests. For example, when you call client.customers.list, you can limit the number of customers returned in each response.

To iterate over all customers, you can use a for loop and the SDK makes additional HTTP requests for you to retrieve additional pages of data.

customers = client.customers.list(
    limit=10,
    sortField="DEFAULT",
    sortOrder="DESC"
)

for customer in customers:
    print(
      f"Customer: ID: {customer.id}, "
      f"Version: {customer.version}, "
      f"Given name: {customer.given_name}, "
      f"Family name: {customer.family_name}"
  )

When an application calls a Square API, it must be able to repeat an API operation when needed and get the same result each time. For example, if a network error occurs while updating a catalog item, the application might retry the same request and must ensure that the item updates only once.

This behavior is called idempotency. Most Square APIs that modify data (create, update, or delete) require you to provide an idempotency key that uniquely identifies the request. This allows you to retry the request if necessary, without duplicating work.

You can provide a custom unique key or simply generate one. There are language specific functions that you can use to generate unique keys. For more information, see Idempotency.

In the following example, you can see how the idempotency_key is generated in a Python application to create an order:

client.orders.create(
    idempotency_key=str(uuid.uuid4()),
    order={
        "location_id": location.id
    }
)

Some Square API resources support versioning. For example, each Customer object has a version field. Initially, the version number is 0. Each update increases the version number. If you don't specify a version number in the request, the latest version is assumed.

This resource version number enables optimistic concurrency; multiple transactions can complete without interfering with each other. As a best practice, you should include the version field in the request to enable optimistic concurrency. The value must be set to the current version. For more information, see Optimistic Concurrency.

The following code example updates a customer name. The client.customers.update method also includes a version number. The method succeeds only if the specified version number is the latest version of the Customer object on the server.

from square.core.api_error import ApiError

try:
    response = client.customers.update(
        customer_id="GZ48C4P2CWVXV7F7K2ZH795RSG",
        given_name="Fred",
        family_name="Jones",
        version=7
    )

    customer = response.customer
    print(
        f"Customer: ID: {customer.id}, "
        f"Version: {customer.version}, "
        f"Given name: {customer.given_name}, "
        f"Family name: {customer.family_name}"
    )

except ApiError as e:
    print(e.status_code)
    print(e.message)

For update operations that support sparse updates, your request only needs to specify the fields you want to change (along with any fields required by the update operation). If you want to clear a field without setting a new value, set its value to None. For more information, see Clear a field with a null.

The following update_location example clears the twitter_username field and sets the website_url field:

client.locations.update(
    location_id="M8AKAD8160XGR",
    location={
        "website_url": "https://developer.squareup.com",
        "twitter_username": None
    }
)

order.update requests require an additional header.

If you're using None to clear fields in an order, you must add the X-Clear-Null: true HTTP header to signal your intention. In the Square Python SDK, the Client class provides an additional_headers parameter that you can use for this purpose:

from square.core import RequestOptions

client.orders.update(
    order_id="A4BMDU4438ZLB",
    order={
        "reference_id": "Order1322",
        "ticket_name": None
    }
    request_options=RequestOptions(
        additional_headers={"X-Clear-Null": "true"}
    )
)