Cheuk Ting Ho
Developer advocate / Data Scientist - support open-source and building the community.
Python Zero to Heros
Online Absolute Beginner Python Tutorials
Every Sunday 1pm (UK time/ BST)
by Cheuk Ting Ho
Get this slide deck: bit.ly/PyFunction
Recap
Python objects - int, float, str, list, dict, bool
Control flows - if-else, for loop, while loop
Any Questions?
Functions
sometime we do the same thing with a different input
e.g. with a different basket print the checkout sum
checkout_sum = sum([catalog[item] for item in shop_list])
print(f"Thank you, the total is £{checkout_sum}")Take some inputs, return an output
def some_func(parameter1, parameter2):
# do something
return resultFunctions
Example: let's write the checkout program as a function
def checkout(shop_list, catalog):
checkout_sum = sum([catalog[item] for item in shop_list])
print(f"Thank you, the total is £{checkout_sum}")
return checkout_sum
my_shop_list = ['toilet paper', 'banana']
shop_catalog = {'toilet paper': 10,
'banana': 0.8,
'coffee beans': 3}
to_pay = checkout(my_shop_list, shop_catalog)Functions
Let's try to find out:
what if we skip the return?
what if we skip a parameter?
Defaults?
def checkout(shop_list, catalog):
checkout_sum = sum([catalog[item] for item in shop_list])
print(f"Thank you, the total is £{checkout_sum}")
return checkout_sum
my_shop_list = ['toilet paper', 'banana']
shop_catalog = {'toilet paper': 10,
'banana': 0.8,
'coffee beans': 3}
to_pay = checkout(my_shop_list, shop_catalog)Functions
Documentation by docstrings:
def checkout(shop_list, catalog):
"""This function calculate how much a customer need to pay.
Parameters
==========
shop_list, list
catalog, dict
Returs
======
checkout_sum, float"""
checkout_sum = sum([catalog[item] for item in shop_list])
print(f"Thank you, the total is £{checkout_sum}")
return checkout_sum
my_shop_list = ['toilet paper', 'banana']
shop_catalog = {'toilet paper': 10,
'banana': 0.8,
'coffee beans': 3}
to_pay = checkout(my_shop_list, shop_catalog)Scopes
It's important to know what variable you are refering to.
Let's do a little experiment
y = 10
def my_func(x):
print(f"inside func, before assign y: {y}")
y = x
print(f"inside func, after assign y: {y}")
print(f"before calling func y: {y}")
my_func(99)
print(f"after calling func y: {y}")Args and Kwargs
Sometimes we are not sure how many parameters
For example:
def total(*args):
return sum(args)
print(total(1,4,10))
Args and Kwargs
similar to args, but you can pass parameters in pairs
For example:
def create_catalog(**kwargs):
result = {}
for key, value in kwargs.items():
result[key] = value
return result
print(create_catalog("toilet paper"=10, "banana"=0.8, "coffee bean"=3))
Modules
Simply speaking a module is a file consisting of Python code
Standard modules e.g.: copy, random, math, os, path
Or add more by installing via pip
Or you can write your own
import other .py file into anothe .py file
Do it by: import / from _ import _ / import _ as
import copy
import pandas as pd
from random import randintLet's write some programs using funcs
1. I randomly pick a fruit from the baskets, I put anything I got in my shopping bag except oranges. I really need some bananas, don't stop till I got one. (random_fruit.py)
2. Tom and Matt both have a shopping list, we want to combine them and remove the redundant items, then calculate how much they spend in total at the end. (combine_checkout.py)
https://github.com/Cheukting/python02hero/tree/master/2020-05-03-python-functions
Homework 📝
Can you using funciton on last weeks homework?
1. one_number_bingo.py: I can buy a ticket for £3 with one number assigned to me at random. It could be any number from 1 to 999. How much do I have to pay to win the game in one situation?
2. one_number_bingo.py (bonus): do Monte Carlo similation to get the average money sepnd instead)
https://github.com/Cheukting/python02hero/tree/master/2020-05-03-python-functions
Next week:
Classes and Instances
Sunday 1pm (UK time/ BST)
There are also Mid Meet Py every Wednesday 1pm
Python Functions and Modules
By Cheuk Ting Ho
