Python

Python

Python is a widely used high-level programming language used for general-purpose programming, created by Guido van Rossum and first released in 1991. Python has a design philosophy which emphasizes code readability. You'll often find that your first guess at what a function is called is surprisingly correct.

For instance, if you want to print something, you write:

print("I'm not dead yet!")

Also, it's true. Python's name is derived from Monty Python.

Python Console

Python has an interactive console you can use in your terminal. Type python3 to get started.

Note: there are two versions: Python2 and Python3. We'll be using Python3. If you ever type simply python in the terminal the terminal will assume you mean Python2. Python3 is better.

Philosophy

The core philosophy of Python is summarized by the document The Zen of Python , which includes aphorisms such as:

• Beautiful is better than ugly

• Explicit is better than implicit

• Simple is better than complex

• Complex is better than complicated

• Readability counts

Familiar Datatypes

Python has all the data types you're used to using in JavaScript. Python has variables, functions, booleans, integers, floats, strings, lists and dictionaries (objects). You never declare var in Python.

This is all legal Python:

my_name = "Steve"
my_age = 2017 - 1988
is_alive = True
my_hobbies = ["board games", "programming", "bikes"]

person = {
  "name": my_name,
  "age": my_age,
  "hobbies": my_hobbies,
}

print(person)
print(person["name"], "has", len(person["hobbies"]), "hobbies.")

Negative String Indexes!!

Python has some little features that make code really sweet to write. Negative string (and array) indexes is simply one example of great syntax options Python offers.

alphabet = "abcdefghijklmnopqrstuvwxyz"
vowels = "aeiou"

# we can use negative numbers to access characters in a string from backwards!
last_letter = alphabet[-1]
third_to_last_letter = alphabet[-3]
print(last_letter, "is the last letter in the alphabet")
print(third_to_last_letter, "is the third to last letter in the alphabet")

# we can use the `in` keyword to see if something is part of a string!
if ("e" in vowels):
  print("yup. that's a vowel.")

Whitespace

Python never uses curly braces to define blocks of code. Instead, it forces programmers to write their code with proper whitespace. Many people find this annoying and you're bound to hear people scoff at Python for this decision.

Here's what a for loop and an if else statement look like in Python. The whitespace is important! You have to consistently indent with tabs, or spaces. Whichever you choose you have to be consistent with how many tabs or spaces you use at each level!

Notice that Python uses a weird word elif for "else if" statements.

for i in range(1, 18):
  if i % 3 == 0 and i % 5 == 0:
    print("divisible by three and five")
  elif i % 3 == 0:
    print("divisible by three")
  elif i % 5 == 0:
    print("divisible by five")
  else:
    print(i)

Functions

Python allows you to define functions with parameters. Parameters can even be declared with default values in case you want to call a function without passing in parameters:

def greet(name="Mysterious Stranger"):
  print("Hello there", name)

greet("Bruce Wayne")
greet()

For Loops

There's no for (var i = 0; i < a.length; i++) for loops in Python. All for loops in Python use automatic iterators, like this:

# traditional for loop
for i in range(0,10):
  print(i)

# backwards for loop, where it goes down by negative one at each step.
for i in range(10, 0, -1):
  print(i)

# a for loop going from 0 to 100 incremented by 17 at each step.
for i in range(0, 100, 17):
  print(i)

Python comes with lots of built in libraries. We're able to import all sorts of useful tools.

Ever wanted to shuffle an array?

import random

cards = ["Ace", "King", "Queen", "Jack", "Ten", "Nine", "Eight"]
print("Original Deck:", cards)
random.shuffle(cards)
print("Shuffled Deck:", cards)

Ever wanted to choose one random thing from a list?

import random

print("Where should I move?")
cities = ["Seattle", "Portland", "San Francisco", "Vancouver"]
city = random.choice(cities)
print("That's it. I'm moving to", city)

That's just a small taste. Let's see what else Python has to offer!