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
   

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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
   

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3. About these Slides
   These slides are deliberately filled with content and can serve as a reference for you.
   2
   

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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
   

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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
   

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6. The standard library
   

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7. Batteries included?
   • pythones comes with a lot of functionality included
   3
   

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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
   

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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
   

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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
    

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11. The package ecosystem
    

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12. What if they did not think about including it?
    6
    

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13. Community
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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
    

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15. Stop talking, give me the code!
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16. Meet Pip
    • (De-facto) standard package manager for python
    • Command-line based
    10
    

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17. $ pip install webexteamssdk
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18. $ pip install --upgrade webexteamssdk
    10
    

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19. $ pip uninstall webexteamssdk
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20. What if I need different versions of the same
    package?
    11
    

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21. Meet Virtualenv
    12
    

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22. $ virtualenv -p python3 test venv
    12
    

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23. $ source test venv/bin/activate
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24. $ pip freeze > requirements.txt
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25. Web Requests
    

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26. Meet requests
    requests
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27. Meet requests
    requests HTTP(S) for Humans
    13
    

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28. Meet requests
    requests HTTP(S) for HumansTM
    13
    

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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 )
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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 ) )
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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
    

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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 ’ ] )
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33. Meet requests (contd.)
    Adding Authentification
    1 import requests
    3 room id = ””
    token = ””
    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 )
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34. The WebexTeamsSDK
    • Often API wrapper exist
    • Let’s rewrite the code above
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35. The WebexTeamsSDK
    • Often API wrapper exist
    • Let’s rewrite the code above
    1 from webexteamssdk import WebexTeamsAPI
    3 room id = ””
    token = ””
    5
    api = WebexTeamsAPI( access token=token )
    7 api . messages . create ( roomId=room id , markdown=” Test12345 ” )
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36. Permanent Storage - Redis
    

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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
    

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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 ’ ) ) )
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39. Questions? Nothing working?
    mneiding@cisco.com
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40. Useful resources
    

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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
    

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