DEVNET-1001 Coding 101: How to Call REST APIs from a REST Client and Python
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The document outlines a session designed for new and returning coders to learn how to call REST APIs from Python, covering basics of REST web services, Python environment setup, and practical examples. Key topics include using Postman to test APIs, structure of REST requests, and sample code for various operations like creating and retrieving policies. Resources for further learning and coding labs are also provided, along with a schedule of related coding classes.
DEVNET-1001 Coding 101: How to Call REST APIs from a REST Client and Python
- 1. Coding Skills 101: How to call REST APIs from Python Amanda Whaley – DevNet Community Manager amwhaley@cisco.com @mandywhaley
- 2. Agenda • Who is this session for? • REST Web Service Basics • Try the APIC-EM APIs from Postman • Python Environment Setup • Python Examples • NEXT UI Toolkit
- 3. Who is Coding 101 for? New coders Returning coders NetOps DevOps
- 4. Congratulations! You have learned: 4 • REST Web Service Basics • Anatomy of a REST API Request • GET and POST • How to call the APIC-EM APIs from Postman • How to call REST APIs from Python • Requests Library
- 5. Disclaimer: Sample Code vs. Real Code 5 The examples and code in this presentation are for Learning and Educational purposes. The samples were created with the goals of clarity and ease of understanding. If you are writing code for a real application, you would write the code in a more efficient and structured style.
- 6. Follow along with the Learning Lab 6 • Login with DevNet/Cisco.com ID • Coding 101 Lab • Coding 102 Lab • Taking it further: Coding 201-207 + APIC-EM Learning Labs Follow Coding 102 instructions to setup your system • Chrome • A text editor (text wrangler, notepad ++, sublime text etc.) • Postman REST Client -- http://www.getpostman.com/ • Python • Go to command prompt and type python3 – did it work? • http://learnpythonthehardway.org/book/ex0.html • Python Requests library -- http://docs.python-requests.org https://learninglabs.cisco.com
- 7. DevNet APIC-EM Always On Sandbox 7 Always there for you to use… • Register on Cisco DevNet (http://developer.cisco.com ) to get the latest information about APIs as they are release • You can use the Always-On APIC-EM Sandbox at anytime • You can use https://learninglabs.cisco.com at anytime https://sandboxapic.cisco.com/
- 8. DevNet GitHub 8 coding-skills-sample-code repository • All the code for this session • All the code for all of the Coding Skills Learning Labs https://github.com/CiscoDevNet
- 9. So what is a REST Web Service? 9 What is a Web Service? – A way for two systems to communicate through a defined interface. – Two major types of Web Services – REST or SOAP What is a REST Web Service? – REST is an architecture style for designing networked applications. – A REST web service is a web service that is as easy to call as making an HTTP request. – RESTful interfaces often offer the CRUD operations
- 10. What is so great about REST? 10 • Hosts • Devices • Policies • Applications Easy to use: • In mobile apps • In console apps • In web apps How does this work? Cisco APIC-EM REST APIs
- 11. How does this work? 8 3rd Party App 3rd Party App Request Response Get Hosts List of Hosts Cisco APIC-EM Cisco APIC-EM
- 12. APIC-EM Example: Get Hosts 12 3rd Party App GET http://{APIC-EMController}/api/v0/host/{start}/{no. rec} List of Hosts returned in JSON Cisco APIC-EM APIC-EM Learning labs Application Policy Infrastructure Controller (APIC) Enterprise Module (EM) Request Response
- 13. Anatomy of a REST Request 13 Method – GET, POST, PUT, DELETE URL – Example: http://{APIC-EMController}/api/v0/host/1/3 Authentication – Basic HTTP, OAuth, none Custom Headers – HTTP Headers – Example: Content-Type: application/json Request Body – JSON or XML containing data needed to complete request JSON -- JavaScript Object Notation, is a lightweight text-based open standard designed for human-readable data interchange.
- 14. Using the API Reference Documentation
- 15. Using the API Reference Documentation
- 16. And what is in the Response? 16 HTTP Status Codes – http://www.w3.org/Protocols/HTTP/HTRESP.html – 200 OK – 201 Created – 500 Internal Error Headers Body – JSON – XML
- 17. REST in Action: How can I try it? 17 HTTP clients can help you quickly test web services Postman - http://www.getpostman.com/ Firefox RestClient - https://addons.mozilla.org/en-US/firefox/addon/restclient/ Command Line using curl - http://curl.haxx.se/docs/httpscripting.html#GET SOAPUI Many IDEs have consoles for testing REST Services built in We are going to use Postman as an example.
- 18. REST Demo – Using Postman 18
- 19. REST Demo – Using Postman 19
- 20. REST Demo – Using Postman 20 Get Hosts – Method: GET – URL: http://APIC-EMController/api/v0/host/{startIndex}/{recordsToReturn} Get Devices – Method: GET – URL: http://APIC-EMController/api/v0/network-device/{startIndex}/{recordsToReturn} Get Policies – Method: GET – URL: http://APIC-EMController/api/v0/policy/{startIndex}/{recordsToReturn} Get Applications – Method: GET – URL: http://APIC-EMController/api/v0/application/{startIndex}/{recordsToReturn}
- 21. REST DEMO – Using the POST or PUT Method 21 To send data to a REST service and either create or update data, you will need to use POST or PUT. Create Policy Example – Method: POST – URL: http://APIC-EMController/api/v0/policy – Custom Headers: Content-Type: application/json – Request Body: JSON that specifies details of new policy What if the Content-Type header is missing? What if there is a mistake in the JSON Request Body? Handy tool for validating JSON -- http://jsonlint.com/
- 22. REST Demo – Using POST or PUT Method 22
- 23. If you didn't receive a 202 Accepted message, check the following: Is your URI correct? Did you choose the method to be Post? Did you remember to specify the Content-Type header as application/json? Did you get a message indicating that the policy already exists? If so, try it again with a different port (please use only high ports) or host. Wait that didn’t work!??!
- 24. Verify that your new policy exists Delete the policy you created Next Steps
- 25. Setup your Python Environment 25 See https://learninglabs.cisco.com : Coding 102 Set up your system instructions A text editor – Text Wrangler, Notepad++, Sublime Text, PyCharm Community Edition etc. Python installed on your system – Preinstalled on many Linux distributions and Mac OS – Windows may need to install - http://python.org/download. – You can check to see if it is installed by typing “python” at a command prompt. Python Requests library – http://docs.python-requests.org/en/latest/user/install/#install Here are some sites that can help you setup your system: – https://wiki.python.org/moin/BeginnersGuide/NonProgrammers – http://learnpythonthehardway.org/book/ex0.html – http://www.codecademy.com/tracks/python
- 26. First REST call from Python 26 #import requests library import requests #specify URL url = 'http://Your-API-EM-Controller/api/v0/host’ #Call REST API response = requests.get(url) #Print Response print response.text Source code file: apic-em1.py
- 27. Python Examples 27 Coding 102 – apic-em1.py – simple example to get list of hosts – apic-em-helloworld.py – “hello world” type example to show list of devices – learning-lab-basics.py – Retrieves device list and pretty prints JSON – learning-lab-basics-step2.py – Retrieves network device list and parses JSON to display networkDeviceId values – learning-lab-basics-step3.py – Retrieves and lists all devices, hosts, policies and configured applications – learning-lab-create-policy.py – Shows how to create a new policy using the POST Method https://github.com/CiscoDevNet/coding-skills-sample-code Download Sample Code
- 28. Python Examples 28 Create a Policy – – Basic steps – 1. Get Hosts – 2. Get Policies – 3. Create a new Policy – 4. Get Policies again to show new one that was added Use POST Method Set Header – Content-Type: application/json What if policy already exists? A unique combination of hostIP, policy name, and ports is required to add a new policy. Source code file: learning-lab-create-policy.py
- 29. learninglabs.cisco.com Coding 201 – Coding 207 Next steps with Python developer.cisco.com Youtube Videos Cisco DevNet Github Get your DevNet Loot reward points! Where to go from here?
- 30. References 30 http://learnpythonthehardway.org/book/ http://docs.python-requests.org/en/latest/index.html https://wiki.python.org/moin/BeginnersGuide/NonProgrammers http://www.codecademy.com/tracks/python https://www.python.org/doc/ http://www.pythonlearn.com/html-008/cfbook014.html http://www.soapui.org/Best-Practices/understanding-rest-headers-and-parameters.html http://www.w3schools.com/jQuery/ http://api.jquery.com/
- 31. Coding Classes all Week in the DevNet Zone https://developer.cisco.com/site/DevNetZone/ Monday Tuesday Wednesday 8-9 am Coding 101 11- 12 pm Coding 203 10-11 am Coding 201 9-10 am Coding 101 1:30 -1 pm Coding 201 Workshop 11- 12 pm Coding 101 12 – 1pm Coding 201 2:30- 3 pm Coding 101 Workshop 11:30 -12 Coding 201 Workshop 1- 2 pm Coding 203 12 -1 pm Coding 210 2:30-3 Coding 101 Workshop 2:30- 3 pm Coding 203 Workshop 2-3 pm Coding 210
- 32. About Me Amanda Whaley • DevNet Community Manager • amwhaley@cisco.com • @mandywhaley • Lives in Austin, TX. • developer.cisco.com • learninglabs.cisco.com “Those who never fail are those who never try.” -- Ilka Chase
- 33. Thank you
Editor's Notes
- #10: REST stands for Representational State Transfer. It relies on a stateless, client-server, cacheable communications protocol (ex. HTTP)
- #14: http://www.json.org/
- #23: Show what happens if you forget the Content-Type Header
- #27: More info on requests library - http://docs.python-requests.org/en/latest/index.html