Learn Python 3

These are my notes from the Learn Python 3 course at Codecademy.

1. Learn Python: Syntax

Print

You can print stuff with print like so:

print("Hello world!")

You can use single quotes too!

print('Single quoties!)

Comments

Comments are preceded with '#' like:

# The code below is totes broken!

Variables

You can create variables with just a variable name and then a value, such as:

age = 12
half_my_age = (my_age / 2)
salutation = "Hola!"
name = "Milton"

Errors

You might encounter a NameError if you try and print a word string but forget the quotes. Python loves quotes dude!

Numbers

An integer (int) is a whole number. No decimal points! It's like 1, 2, 3, etc. If you're counting member of a team, cookies in a jar or keys on a keyboard, use integers.

A floating-point (float) number is a decimal number. You can use it to measure the length of a house, average test scores or a baseball player's batting average.

Calculations

You can calculate stuff like this:

print(5 * 5 * 18 * 183 / 14)

Exponents

Here's an example:

# 5 to the 10th power
print(5 ** 10)

Modulo

Modulo is indicated by % and indicates the remainder of a division calculation.

some_important_number = (27 % 4)
print()

Concatenation

Add two things together! Like:

string1 = "My name is "
string2 = "Inigo Montoya. "
string3 = "You killed my father. "
string4 = "Prepare to die."

# Define message below:
message = string1 + string2 + string3 + string4

print(message)

Plus Equals

This is a shorthand for updating variables. Example:

total_miles = 0
miles_i_walked_today = 15
miles_i_walked_yesterday = 5
total_miles += miles_i_walked_today
total_miles += miles_i_walked_yesterday
print(total_miles)
# Should print 20!

Multiline strings

You can start and end big blocks of code with three tick marks!

This is a huge block of code and wow it's really long and stuff like that and it's so long and really long and long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long long

Practice exercise: Create Purchasing Information and Receipts for Lovely Loveseats

Not 100% sure this is right, but taking a swing at this (it won't make sense unless you can follow along with the Codecademy exercise)

lovely_loveseat_description = ('''Lovely Loveseat. Tufted polyester blend on wood. 32 inches high x 40 inches wide x 30 inches deep. Red or white.''')

lovely_loveseat_price = 254.00

stylish_settee_description = ('''Stylish Settee. Faux leather on birch. 29.50 inches high x 54.75 inches wide x 28 inches deep. Black.''')

stylish_settee_price = 180.50

luxurious_lamp_description = ('''Luxurious Lamp. Glass and iron. 36 inches tall. Brown with cream shade.''')

luxurious_lamp_price = 52.15

sales_tax = .088

customer_one_total = 0

customer_one_itemization = ""

customer_one_itemization += lovely_loveseat_description

customer_one_total += luxurious_lamp_price

customer_one_tax = customer_one_total * sales_tax
customer_one_total += customer_one_tax
print("Customer One Items:")
print(customer_one_itemization)
print("Customer One Total:")
print(customer_one_total)

2. Learn Python: Functions

A function is a collection of several lines of code. If you use a function, you can call a bunch of those lines of code at once without sounding like a broken record!

Typically if we're going to print a bunch of lines in a row, we do this:

 print("Some day we'll find it")
  print("The rainbow connection")
  print("The lovers, the dreamers...")
  print("...and me!")

What you can do is use def rainbow_connection(): ahead of the print lines to store the whole song as rainbow_connection:

def rainbow_connection():
  print("You may say I'm a dreamer")
  print("But I'm not the only one")
  print("I hope some day you'll join us")
  print("And the world will be as one")

Then you can simply call it with rainbow_connection();

Write a function

This was just more practice, like this:

def loading_now():
  print("Please wait!  This page is loading...")

loading_screen();

Handling white space

When definite a function, everything that is properly intended (Codecademy uses spaces, other people use tabs...I'm not experienced enough to have a preference yet!) gets printed. For example, the following will print "We will we will rock you!":

def rock_you():
  print("We will")
  print("We will")
  print("rock you!")    

rock_you();

But this will print "rock you!" first, and then "We will we will"

def rock_you():
  print("We will")
  print("We will")
print("rock you!")    

rock_you();

Note to self: I don't fully understand why.

Parameters

This is all about adding including variables (parameters) that will change in code. For example

def food_is_fun(todaysspecial):
  print("Today's special is " + todaysspecial + ".")
  
food_is_fun("pizza");

You could then put different food in quotes like "ice cream" or "veggies."

Multiple Parameters

Kind of the same idea but with multiple things. Take this for instance:

def fav_foods(fav1,fav2,fav3):
 print("My favorite foods are " + fav1 + ", " + fav2 + ", and " + fav3 + ".")

fav_foods("pizza", "ice cream", "pickle chips");

This will print "My favorite foods are pizza, ice cream, and pickle chips."

Left off at keyword arguments! https://www.codecademy.com/courses/learn-python-3/lessons/intro-to-functions/exercises/keyword-arguments