python for Beginners - Part 2 Pythons Package Ecosystem Marcel Neidinger Associate Solutions Engineer, Collaboration [email protected] 14. November 2019 

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 

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

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 

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 

The standard library 

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

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 

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 

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 

The package ecosystem 

What if they did not think about including it? 6 

Community 7 

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 

Stop talking, give me the code! 9 

Meet Pip • (De-facto) standard package manager for python • Command-line based 10 

$ pip install webexteamssdk 10 

$ pip install --upgrade webexteamssdk 10 

$ pip uninstall webexteamssdk 10 

What if I need different versions of the same package? 11 

Meet Virtualenv 12 

$ virtualenv -p python3 test venv 12 

$ source test venv/bin/activate 12 

$ pip freeze > requirements.txt 12 

Web Requests 

Meet requests requests 13 

Meet requests requests HTTP(S) for Humans 13 

Meet requests requests HTTP(S) for HumansTM 13 

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 

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 

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 

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 

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 ) 16 

The WebexTeamsSDK • Often API wrapper exist • Let’s rewrite the code above 17 

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 ” ) 17 

Permanent Storage - Redis 

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 

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 

Questions? Nothing working? [email protected] 19 

Useful resources 

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