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Introducing Support for oneOf and anyOf in Python SDKs

· 5 min read

We are introducing the special oneOf and anyOf types in our Python SDKs.


In OpenAPI, any request parameter or response payload could use union types i.e. OneOf/AnyOf, which provides the flexibility of accepting different types of request parameters and returning various types of response payload. Here is an example of an API call using union types,

summary: Create a new user
operationId: createUser
required: true
- $ref: '#/components/schemas/Accountant'
- $ref: '#/components/schemas/Manager'
description: User created successfully
- $ref: '#/components/schemas/AccountantResponse'
- $ref: '#/components/schemas/ManagerResponse'

The API call, shown in the OpenApi format above, is a post-call that takes in either Accountant or Manager as request payload. Previously, union-types were not supported therefore the endpoint was expecting the combined schema UsersCreateRequest as a parameter. Here is how the parameter initialization would look like when calling the endpoint,

body = Accountant(

response = client.user_controller.create_user(body)

Now let's look at the response type of the same API call in the following example,

response = client.user_controller.create_user(body)

assert isinstance(response, AccountantResponse) # True
assert isinstance(response, ManagerResponse) # False

In the above code snippet, createUser will return either the AccountantResponse or ManagerResponse instance as response payload. Previously, it was considered a dynamic response which allowed any type of response payload. Now, with the introduction of OneOf and AnyOf support, we can assert that the response can be of either AccountantResponse or ManagerResponse.

What has Changed?

The Python SDK now has the ability to handle union types in an endpoint's request and response. The type validation for union types is also added to support the OneOf/AnyOf constraints.

Introducing UnionTypeLookUp

All union types (i.e. OneOf/AnyOf) instances defined in the spec are now being accessed through UnionTypeLookUp. We introduced a class in utilities by the name of UnionTypeLookUp which holds a dictionary of unionTypes. The responsibility of the UnionTypeLookUp class is to provide the already in-place union-type instances. The instance returned by the UnionTypeLookUp class, is then used for validation, deserialization, and serialization.

For the given endpoint, the union-type instance would look like,

'CreateUserBody': AnyOf(
'CreateUserResponse': OneOf(

Changes in Models:

Now, any custom type (i.e. models or enums) participating as union-type, has the validate method to verify all required properties are present in the case of models and the provided value is a valid enum value in the case of enums.

Changes in Endpoints:

Endpoint Doc Changes:

The endpoint's doc string has been updated to describe union-type parameters or return types.

def create_user(self,
"""Does a POST request to /users/create.

Create a new user

body (Accountant | Manager): TODO: type description here.

AccountantResponse | ManagerResponse: Response from the API. User
created successfully

APIException: When an error occurs while fetching the data from
the remote API. This exception includes the HTTP Response
code, an error message, and the HTTP body that was received in
the request.


Parameter Validation:

The union-type parameters are now being validated when sending the request.

return super().new_api_call_builder.request(
.validator(lambda value: UnionTypeLookUp.get('CreateUserBody').validate(value)))

Response Deserialization:

The union-type response is now being validated and then deserialized.

return super().new_api_call_builder.response(
.deserializer(lambda value: APIHelper.deserialize_union_type(
UnionTypeLookUp.get('CreateUserResponse'), value))

Validation Exceptions:

We have introduced OneOfValidationException and AnyOfValidationException which will be thrown whenever an input with an invalid type is provided to an endpoint or invalid typed data is received via a response from the server. This feature will enforce type strictness and validation of requests and responses within the SDK.

Following are the trigger points for raising these exceptions:

OneOfValidationException: It is raised when either more than one type is matched or no type is matched at all against the provided value.

AnyOfValidationException: It is raised when no type matched at all against the provided value. You can explicitly rescue the OneOfValidationException and AnyOfValidationException in the code snippet.

result = client.user_controller.create_user(body)
except OneOfValidationException as e:
except AnyOfValidationException as e:
except APIException as e:

README Changes:

Now, the Python SDK README will reflect the support for union types in parameter types or response types.


Portal Changes

We have added the capability to select and configure any case mentioned as union type through our API Code Playground on the portal. With this feature, you can now generate code samples for different cases of union types.

portal changes