PyLadies

Vienna 2024-01-16

Agenda for today

1. What is API, REST API
2. How to use already created API with Requests

What is an API

• Application programming interface
• Way to interact between software components
• Get data
• Send data
• Perform actions
• Web API
• Defined interface
• Hiding the complexity from the user

What is an API

• Abstraction
• Communicating through protocol
• E.g. - twitter API, way how to get tweets from twitter and have fun with them
• API exist basically for everything
• Today: Focus on one type of REST-API

REST API

• REpresentational State Transfer
• Modelled after the web itself
• Resources to interact with under an URL�for example: https://en.wikipedia.org/wiki/Python
• Page loads representation in a self-describing format
• Contains links to other pages

REST API

• General principles:
• Client–server, Stateless, Cacheable, Uniform interface, Layered system
• Often implemented using HTTP and URLs

REST API usage example with HTTP

REST API usage example with HTTP

Client sends message to server:

• GET /book/9780394713519

Server responds:

• {“author”: “Angela Davis”, “title”: “Women, Race & Class”}

Resource

• Represents any object in your world
• e.g. blog post, user account, physical location, a company, …
• Has URL (unique address)
• Resource representation - state of the resource in certain time
• → consist of Data, Metadata and Hypermedia links
• View in different media types

Media type examples

• clients (your web browser) decide what to do with a resource based on announced media type
• application/json, audio/mpeg, text/html, image/jpeg, video/mp4, text/plain

online database of official MIME types

Example API Url

Resource Methods

• Type of request you can make on resource
• 5 basic types
• GET - retrieve information
• e.g.: GET /wiki/Python

Resource Methods

• DELETE - method removes a resource
• POST - create a new resource (“post” a message)
• PUT - update or create a resource
• PATCH - change parts of a resource

HTTP response status codes

• Code to tell you if the request was successful
• 5 main categories, distinguished by first digit
• 1xx informational response, 2xx successful, 3xx redirection, 4xx client error, 5xx server error
• Common examples - 200, 404, 403, 500, 502
• when getting external API, check for 2xx or 3xx code
• https://http.cat

OpenAPI/Swagger API documentation

• Resource representation should be self documenting, but most aren’t
• OpenAPI/Swagger is a system for documenting explicitly:
• What types resources are there
• How can you interact with them
• Which fields do they have
• link for API documentation
• Swagger petstore example

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Token authorization of requests

• API owners usually prevent whole internet do connect
• Authentication e.g. via tokens
• Create account on web page of API and create a token (=machine password)
• Use this access token in all other requests usually in header

Requests

• Python module that allows you to send HTTP requests
• Return a Response Object with all the response data
• Support all methods (get, post, …)
• Very widely used
• list of properties and methods https://www.w3schools.com/python/ref_requests_response.asp

Demo

https://colab.research.google.com/drive/11zFpt19H6FtFr8kTaI2XmPqzi6ERNOcv?usp=sharing

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Sum it up

• APIs allow you to interact with the world�and to get interesting data�and process it in a program
• REST is a common architecture type
• Often using HTTP to communicate
• About resources identified by URLs

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Thank you for patience

Happy coding!