Python for Systems Engineers - Part 2

Python is one of the most popular programming languages of our time and the powerhouse behind most of Cisco’s API efforts. If there is a Cisco API chances are high that there will be a software development kit for that API in python. In this 3-part webinar series we will get our hands dirty with python.

Part 2 covers the python package ecosystem, virtual environments and some packages that might be useful when developing proof-of-concepts.

Transcript

1. python for Beginners - Part 2 Pythons Package Ecosystem Marcel Neidinger Associate Solutions Engineer, Collaboration mneiding@cisco.com 14. November 2019
2. What is the plan? • Part 1: Introduction to python3 • Part 2: Introduction to some useful python packages • Part 3: Hands-On - Let’s code a small MVP in one hour 1
3. About these Slides These slides are deliberately filled with content and can serve as a reference for you. 2
4. About these Slides These slides are deliberately filled with content and can serve as a reference for you. Code sample 1 p r i n t ( ” This i s a code snippet ” ) Exercise 2
5. About these Slides These slides are deliberately filled with content and can serve as a reference for you. Code sample 1 p r i n t ( ” This i s a code snippet ” ) Exercise Exercise: Some trivial proofs Proof, for any decission problem P1 ∈ NP and P2 ∈ P that P1 >p P2 holds. 2
6. The standard library
7. Batteries included? • pythones comes with a lot of functionality included 3
8. Build-in functions • Don’t reinvent the wheel! • → Your programming skills are (very probably) worse then those who implemented the standard libary • Batteries included programming 4
9. json - Parsing and Creating json 1 import json • Load a json string into a dict 1 j s o n s t r = ’ { ” best−api ” : ”Webex Teams API ” } ’ res = json . loads ( j s o n s t r ) 3 p r i n t ( ” The best API i s ” + s t r ( res [ ’ best−api ’ ] ) ) 5
10. json - Parsing and Creating json 1 import json • Load a json string into a dict 1 j s o n s t r = ’ { ” best−api ” : ”Webex Teams API ” } ’ res = json . loads ( j s o n s t r ) 3 p r i n t ( ” The best API i s ” + s t r ( res [ ’ best−api ’ ] ) ) • Create json from a dict 1 d = { ’message ’ : ” Hi , I am a message ” , ’ toPersonEmail ’ : ” jgomez2@cisco .com” } json representation = json . dumps( d ) 3 p r i n t ( json representation ) 5
11. The package ecosystem
12. What if they did not think about including it? 6
13. Community 7
14. Meet PyPi • Central repository for python code • 204 720 projects (2 of them from me) • 1 540 109 releases • 2 294 855 files • 385 989 user 8
15. Stop talking, give me the code! 9
16. Meet Pip • (De-facto) standard package manager for python • Command-line based 10
17. $ pip install webexteamssdk 10
18. $ pip install --upgrade webexteamssdk 10
19. $ pip uninstall webexteamssdk 10
20. What if I need different versions of the same package? 11
21. Meet Virtualenv 12
22. $ virtualenv -p python3 test venv 12
23. $ source test venv/bin/activate 12
24. $ pip freeze > requirements.txt 12
25. Web Requests
26. Meet requests requests 13
27. Meet requests requests HTTP(S) for Humans 13
28. Meet requests requests HTTP(S) for HumansTM 13
29. Meet requests (Contd.) Making a GET request 1 import requests response = requests . get ( ” https : / / deckofcardsapi .com/ api / deck / new / s h u f f l e / ” ) 3 p r i n t ( response . status code ) 14
30. Meet requests (Contd.) Making a GET request 1 import requests response = requests . get ( ” https : / / deckofcardsapi .com/ api / deck / new / s h u f f l e / ” ) 3 p r i n t ( response . status code ) Accessing the json 1 import requests response = requests . get ( ” https : / / deckofcardsapi .com/ api / deck / new / s h u f f l e / ” ) 3 payload = response . json ( ) deck = payload [ ’ deck id ’ ] 5 p r i n t ( ” The id of our deck of cards i s : ” + s t r ( deck ) ) 14
31. Meet requests (contd.) Making a POST request (with data) 1 import requests payload = { ” deck count ” : 4} 3 response = requests . post ( ” https : / / deckofcardsapi .com/ api / deck / new / s h u f f l e / ” , data= payload ) deck = response . json ( ) [ ’ deck id ’ ] 15
32. Meet requests (contd.) Making a POST request (with data) 1 import requests payload = { ” deck count ” : 4} 3 response = requests . post ( ” https : / / deckofcardsapi .com/ api / deck / new / s h u f f l e / ” , data= payload ) deck = response . json ( ) [ ’ deck id ’ ] Draw a card import requests 2 deck = response . json ( ) [ ’ deck id ’ ] 4 u r l = ” https : / / deckofcardsapi .com/ api / deck / ” + s t r ( deck ) + ” / draw /? count=2 ” 6 resp = requests . get ( u r l ) r e s u l t = resp . json ( ) 8 f o r card in r e s u l t [ ’ cards ’ ] : p r i n t ( ”We got a ” + card [ ’ s u i t ’ ] + ” ” + card [ ’ value ’ ] ) 15
33. Meet requests (contd.) Adding Authentification 1 import requests 3 room id = ”<INSERT ROOM ID HERE>” token = ”<INSERT TOKEN HERE>” 5 headers = { 7 ” Authorization ” : ” Bearer ” + s t r ( token ) } 9 payload = { 11 ” markdown ” : ” Hello from ∗∗python ∗∗ ” , ” roomId ” : room id , 13 } a p i u r l = ” https : / / api . ciscospark .com/ v1 / messages ” 15 resp = requests . post ( a p i u r l , headers=headers , data=payload ) 16
34. The WebexTeamsSDK • Often API wrapper exist • Let’s rewrite the code above 17
35. The WebexTeamsSDK • Often API wrapper exist • Let’s rewrite the code above 1 from webexteamssdk import WebexTeamsAPI 3 room id = ”<INSERT ROOM ID HERE>” token = ”<INSERT TOKEN HERE>” 5 api = WebexTeamsAPI( access token=token ) 7 api . messages . create ( roomId=room id , markdown=” Test12345 ” ) 17
36. Permanent Storage - Redis
37. Meet Redis • Remote Dictionary Server • High performance key-value store • Side-note: Start a Redis instance with 1 $ docker run −−name=redis −devel −−publish =6379:6379 −−hostname=redis −−r e s t a r t =on− f a i l u r e −−detach redis : l a t e s t 18
38. Meet redis (contd.) Connect to redis and set/get a key 1 import redis 3 r = redis . Redis ( ) r . set ( ” test key ” , ” This i s a t e s t key ” ) 5 res = r . get ( ” test key ” ) i f res i s not None : 7 p r i n t ( ” The value i s ” + s t r ( res . decode ( ’ utf −8 ’ ) ) ) 19
39. Questions? Nothing working? mneiding@cisco.com 19
40. Useful resources
41. Links • The python3 standard library: https://docs.python.org/3/library/ • Installing python for development: Mac: https://docs.python-guide.org/starting/install3/osx/ Windows: https://docs.python-guide.org/starting/install3/win/ Linux: https://docs.python-guide.org/starting/install3/linux/ • The core concepts of python: https://www.python-course.eu/python3_history_and_philosophy.php • Setup the atom editor for python development: https://hackernoon.com/ setting-up-a-python-development-environment-in-atom-466d7f48e297