api-client 1.0.1

Separate the high level client implementation from the underlying CRUD.

Python Client Abstraction

I have often found that I am constantly writing similar clients to in order to provide an abstraction around a third party API.

This client abstraction aims to reduce the overhead of writing the client, and should allow the consumer of the APIs to focus on the high level implementation, rather than the design of the client itself.

Installation

pip install api-client

Usage

from apiclient import BaseClient
from apiclient.decorates import endpoint


# Define endpoints, using the provided decorator.
@endpoint(base_url="https://jsonplaceholder.typicode.com")
class Endpoint:
    todos = "todos"
    todo = "todos/{id}"


# Extend the client for your API integration.
class JSONPlaceholderClient(BaseClient):

    def get_all_todos(self) -> dict:
        return self.read(Endpoint.todos)

    def get_todo(self, todo_id: int) -> dict:
        url = Endpoint.todo.format(id=todo_id)
        return self.read(url)


# Initialize the client with the correct authentication method,
# response handler and request formatter.
>>> client = JSONPlaceholderClient(
    authentication_method=HeaderAuthentication(token="<secret_value>"),
    response_handler=JsonResponseHandler,
    request_formatter=JsonRequestFormatter,
)


# Call the client methods.
>>> client.get_all_todos()
[
    {
        'userId': 1,
        'id': 1,
        'title': 'delectus aut autem',
        'completed': False
    },
    ...,
    {
        'userId': 10,
        'id': 200,
        'title': 'ipsam aperiam voluptates qui',
        'completed': False
    }
]


>>> client.get_todo(45)
{
    'userId': 3,
    'id': 45,
    'title': 'velit soluta adipisci molestias reiciendis harum',
    'completed': False
}


# REST APIs correctly adhering to the status codes to provide meaningful
# responses will raise the appropriate exeptions.
>>> client.get_todo(450)
NotFound: 404 Error: Not Found for url: https://jsonplaceholder.typicode.com/todos/450

>>> try:
...     client.get_todo(450)
... except APIClientError:
...     print("All client exceptions inherit from APIClientError")
"All client exceptions inherit from APIClientError"

BaseClient Interface

The BaseClient provides the following public interface:

• create(self, endpoint: str, data: dict)

  Delegate to POST method to send data and return response from endpoint.

• read(endpoint: str, params: OptionalDict = None)

  Delegate to GET method to get response from endpoint.

• replace(endpoint: str, data: dict, params: OptionalDict = None)

  Delegate to PUT method to send and overwrite data and return response from endpoint.

• update(endpoint: str, data: dict, params: OptionalDict = None)

  Delegate to PATCH method to send and update data and return response from endpoint

• delete(endpoint: str, params: OptionalDict = None)

  Delegate to DELETE method to remove resource located at endpoint.

• get_exception_map() -> dict

  If not overridden will use the default dictionary defined to map bad response status codes into the relevant exceptions. Users can customize the exceptions raised by overriding this method.

• get_request_timeout() -> float

  By default, all requests have been set to have a default timeout of 10.0 s. This is to avoid the request waiting forever for a response, and is recommended to always be set to a value in production applications. It is however possible to override this method to return the timeout required by your application.

Authentication Methods

Authentication methods provide a way in which you can customize the client with various authentication schemes through dependency injection, meaning you can change the behaviour of the client without changing the underlying implementation.

The apiclient supports the following authentication methods, by specifying the initialized class on initialization of the client, as follows:

client = ClientImplementation(
   authentication_method=<AuthenticationMethodClass>(),
   response_handler=...,
   request_formatter=...,
)

NoAuthentication

This authentication method simply does not add anything to the client, allowing the api to contact APIs that do not enforce any authentication.

QueryParameterAuthentication

This authentication method adds the relevant parameter and token to the client query parameters. Usage is as follows:

authentication_method=QueryParameterAuthentication(parameter="apikey", token="secret_token"),

Example. Contacting a url with the following data

http://api.example.com/users?age=27

Will add the authentication parameters to the outgoing request:

http://api.example.com/users?age=27&apikey=secret_token

HeaderAuthentication

This authentication method adds the relevant authorization header to the outgoing request. Usage is as follows:

authentication_method=HeaderAuthentication(token="secret_value")

# Constructs request header:
{"Authorization": "Bearer secret_value"}

The Authorization parameter and Bearer scheme can be adjusted by specifying on method initialization.

authentication_method=HeaderAuthentication(
   token="secret_value"
   parameter="Foo",
   scheme="Bar",
)

# Constructs request header:
{"Foo": "Bar secret_value"}

Or alternatively, when APIs do not require a scheme to be set, you can specify it as a value that evaluates to False to remove the scheme from the header:

authentication_method=HeaderAuthentication(
   token="secret_value"
   parameter="Foo",
   scheme=None,
)

# Constructs request header:
{"Foo": "secret_value"}

BasicAuthentication

This authentication method enables specifying a username and password to APIs that require such.

authentication_method=BasicAuthentication(username="foo", password="secret_value")

Response Handlers

Response handlers provide a standard way of handling the final response following a successful request to the API. These must inherit from BaseResponseHandler and implement the get_request_data() method which will take the requests.Response object and parse the data accordingly.

The apiclient supports the following response handlers, by specifying the class on initialization of the client as follows:

client = ClientImplementation(
   authentication_method=...,
   response_handler=<ResponseHandlerClass>,
   request_formatter=...,
)

RequestsResponseHandler

Handler that simply returns the original Response object with no alteration.

JsonResponseHandler

Handler that parses the response data to json and returns the dictionary. If an error occurs trying to parse to json then a UnexpectedError will be raised.

XmlResponseHandler

Handler that parses the response data to an xml.etree.ElementTree.Element. If an error occurs trying to parse to xml then a UnexpectedError will be raised.

YamlResponseHandler

Handler that parses the response data in yaml format and returns the dictionary. If an error occurs trying to parse the yaml then an UnexpectedError will be raised.

Request Formatters

Request formatters provide a way in which the outgoing request data can be encoded before being sent, and to set the headers appropriately.

These must inherit from BaseRequestFormatter and implement the format() method which will take the outgoing data object and format accordingly before making the request.

The apiclient supports the following request formatters, by specifying the class on initialization of the client as follows:

client = ClientImplementation(
   authentication_method=...,
   response_handler=...,
   request_formatter=<RequestFormatterClass>,
)

JsonRequestFormatter

Formatter that converts the data into a json format and adds the application/json Content-type header to the outoing requests.

Exceptions

All exceptions raised as part of the apiclient inherit from APIClientError. In order to comply with REST API standards, exceptions have been split into a granular level, allowing the user to map direct exceptions easily. Exceptions have been split into the following groups.

RedirectionError

A redirection status code was returned as a final code when making the request. This means that no data can be returned to the client as we could not find the requested resource as it had moved.

The following exceptions inherit from RedirectionError:

• MultipleChoices
• MovedPermanently
• Found
• SeeOther
• NotModified
• UseProxy
• TemporaryRedirect
• PermanentRedirect

ClientError

The client was used incorrectly for contacting the API. This is due primarily to user input by passing invalid data to the API.

The following exceptions inherit from ClientError:

• BadRequest
• Unauthorized
• PaymentRequired
• Forbidden
• NotFound
• MethodNotAllowed
• NotAcceptable
• ProxyAuthenticationRequired
• RequestTimeout
• Conflict
• Gone
• LengthRequired
• PreconditionFailed
• RequestEntityTooLarge
• RequestUriTooLong
• UnsupportedMediaType
• RequestedRangeNotSatisfiable
• ExpectationFailed
• UnprocessableEntity
• Locked
• FailedDependency
• UpgradeRequired
• PreconditionRequired
• TooManyRequests
• RequestHeaderFieldsTooLarge

ServerError

The API was unreachable when making the request.

The following exceptions inherit from ServerError:

• InternalServerError
• NotImplemented
• BadGateway
• ServiceUnavailable
• GatewayTimeout
• HttpVersionNotSupported
• VariantAlsoNegotiates
• InsufficientStorage
• LoopDetected
• NotExtended
• NetworkAuthenticationRequired

UnexpectedError

An unexpected error occurred when using the client. This will most likely be the result of another exception being raised. If possible, the original exception will be indicated as the causing exception of this error.

Endpoints

The apiclient also provides a convenient way of defining url endpoints with use of the @endpoint decorator. In order to decorate a class with @endpoint the decorated class must define a base_url attribute along with the required resources. The decorator will combine the base_url with the resource.

Example:

from apiclient.decorates import endpoint

@endpoint(base_url="http://foo.com")
class Endpoint:
    resource = "search"

>>> Endpoint.resource
"http://foo.com/search