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The Basics

Created By: Sean Boerhout

Variables and Data Types

So where do we start? Well, nearly all programming involves variables, or snippets of memory in your computer that holds some data. Say I wanted to take user input, or record the number of times someone pressed a button. You'd need variables to do this!

Let's start with a simple example: the number of minecraft worlds I have on my computer to date, which is 27. 

minecraft_world_count = 27
Here, minecraft_world_count is my variable, and it holds a number (an integer to be exact). Different types of data need to be held with different types of variables; for example, 1.1 isn't an integer anymore, it's a rational number (in coding terms, a floating-point number).

Another cool thing in python is that you can easily represent large numbers. Whenever you assign a number to a variable, you can't use commas to make it easily readable. For example, 

myNumber = 100,000

Will actually cause python to think that your number is of type tuple, which is a data type that doesn't allow you to change its value. To tell python that the number is still an integer you can do this:

my_number = 100_00

Printing

Now, suppose I wanted to print the value of a variable as an output. Python has a useful function called print() for this, so 

print(myNumber)

will output 100000.

If I wanted to combine a string with the number, all you need to do is pass another argument (what print() will print) to print().

print("My number is ", myNumber)
Output: 
My number is 100000

One more thing: what if we wanted to format a string into different parts i.e. number here, string there without using commas? Python allows us to do this super easily too:

print(f"My number is { myNumber }")
Output: 
My number is 100000
Python recognizes that you wanted a formatted string by prefixing the string with an f. Then you can use curly braces to say where you want the number! (You'll see how awesome this is in future lessons).

Strings

Say I wanted to give my favorite world a name, and hold that name in a variable. I could do it like this: 

minecraft_world_name = "Zombie manhunt"
And in this case, the variable would be of type string.

In python, strings are neat because you can add characters to them like this:

my_name = "Bill"
my_full_name = my_name + " Mitchell"
print(my_full_name)
Output: 
Bill Mitchell

There are also some cool methods to modify strings:

  • Makes a string uppercase

rock = "let's rock"
print(rock.upper())
Output: 
LET'S ROCK

  • Makes a string lowercase

fruit = "APPLES"
print(fruit.lower())
Output: 
apples

  • Capitalizes a string

my_name = "bill mitchell"
print(my_name.title())
Output: 
Bill Mitchell

Booleans

One more example: suppose I wanted to say whether python is cool. I could use a boolean type variable: python_is_awesome = True

Type Function

If you ever want to know what the type of something is, then you can use a function called type(). This outputs the type of the variable:

print(type(1))
print(type(1.1))
print(type(1000000000))
print(type("one"))
print(type([1,2,3,4]))  # Coming next lesson!
Output: 
<type 'int'>
<type 'float'>
<type 'int'>
<type 'str'>
<type 'list'>

Basic Arithmetic

So... pure variables are boring - you've probably figured that out by now. Can we modify them?

In fact, yes! And it's super easy. Whenever you modify a variable, python essentially overrides one of the variables. Say I just made a new minecraft world. To add another world, I'd just do:

minecraft_world_count = minecraft_world_count + 1

Super easy! Since programmers use this kind of arithmetic very often, however, there is shorthand notation for this:

minecraft_world_count += 1

+= # variable = variable + increment
-= # variable = variable - increment
*= # variable = variable * increment
/= # variable = variable / increment

Commenting

What if you have code and you want to write a description about it? Just writing next to it won't work because python will think that you're still trying to code. In this case, you can use comments. Simply prefix any words/sentences/phrases with a hashtag: #. For bulk commenting, you can use three quotes.

Example: 

# My name is Zephyr:
print("My name is Zephyr!")

"""
Do you like striders in minecraft?
I do... they are fun, but could use
more health. On a scale of 1-10, 
this is how much I like striders:
"""
print(7)

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