Separate the high level client implementation from the underlying CRUD.
Project description
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"
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
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