Python Variables

Introduction

We now have everything set up ready to start learning some Python!

Note

There are many other excellent Python beginner’s tutorials available for free on the internet, such as:

• https://www.w3schools.com/python/default.asp

• https://python.land/python-tutorial

My tutorials are going to focus on quickly getting into interacting with the world of Minecraft. We won’t be going into programming theory in detail.

Therefore, a tutorial like w3schools will be needed to fill in the background if you want a deeper understanding of the language.

Follow along with these tutorials by having both your Minecraft client and your VSCode windows visible on your screen. You should try out the Python commands shown here and feel free to experiment.

Each time you come back to work on these tutorials you can get yourself ready to go by following Setup for each Tutorial.

Variables, Types and Operators

Variables provide a place to hold some bit of data for use inside of a computer program. They have the following properties:

• Name: a name that is used to identify the variable.

• Value: the data that the variable holds.

• Type: the type of data that the variable holds.

• Scope: in which parts of the code this variable is available.

Note

Scope is a moderately advanced concept which you can ignore for the moment. Advanced topics like this will be covered in the explanations section. I suggest skipping anything in the explanations section on your first read through the tutorials and then come back later when you have a better understanding of the fundamentals.

Operators are used to make changes to variables. For example the = operator assigns a value to a variable, and the + operator adds two variables together.

In Python we can easily create a variable using assignment. This table below shows some Python assignment commands using the = operator.

examples of creating variables in Python

Command	Name	Value	Type
birth_year = 1964	birth_year	1964	int (a whole number)
my_height = 1.94	my_height	1.94	float (a decimal number)
my_name = “giles”	my_name	“giles”	str (a string of characters)

Note that Python can automatically work out what type of variable you are creating. e.g. it recognizes that using quotes means I want a string of characters. This w3schools variables page has further examples.

Trying out Variables

Try out the commands below by typing them into the iPython prompt in your VSCode terminal window. Note that input [4] just asks iPython to show the values of the 3 variables you created:

In [1]: birth_year = 1964

In [2]: my_height = 1.94

In [3]: my_name = "giles"

In [4]: birth_year, my_height, my_name
Out[4]: (1964, 1.94, 'giles')

Let’s try another operator - or minus. This operator subtracts the value of one variable from another. It behaves just like - in basic arithmetic. Try out the commands below:

In [6]: age = 2022 - birth_year

In [7]: age
Out[7]: 58

This makes a calculation from the value 2022 and the value of the variable birth_year and assigned it to variable age. Interactive Python will always print the value returned by the last command you input, so in Out[7] age evaluates to 58.

Variables in Minecraft

MCIWB provides some built in variables that you can use. The most important is called world and it is your entry point into many of the functions provided by the library.

world is a special type of variable called an object which can have many values stored in its properties. Objects can also have methods which execute code.

One property of world is player. player is also an object and it has a property called pos which holds the player’s current position.

You can access the player’s location like this:

In [10]: world.player.pos
Out[10]: Vec3(x=633, y=73, z=-1665)

out[10] shows the player’s current position is x=633, y=73, z=-1665.

Try moving your player around and see how the position changes by repeating the above command.

Note

You will notice that the position is reported as a type of variable called Vec3.

Vec3 holds the Minecraft coordinates that you may be familiar with if you have used e.g. the teleport command.

For advanced detail on what this all means see Minecraft’s Coordinate System.

An example of a method on world is set_block which will place a block in a particular position.

Make sure your player is standing on the flat area of sand and execute the set_block method like this:

pos = world.player.pos
world.set_block(pos, Item.IRON_BLOCK)

Your player should have been bumped out of their position and if you turn around you will see an iron block.

What you did here was assign your player’s position to the variable pos and then called the set_block method on world. You told set_block to use pos for the position and IRON_BLOCK for the block to place.

Item is another built-in variable that you can use. It is a list of all the types of blocks in Minecraft. If you type Item.IR in iPython and then hit Tab you will see a list of all the items in Minecraft that begin with IR. See Command Completion for more details.

Iron Golem

OK, let’s make an iron golem! Copy and paste the following Python code commands into the Python terminal:

Note

To copy and paste code from this page to your terminal:

• Drag the mouse to highlight the code you want to Copy

• right click the highlight and click Copy to copy the code to the clipboard

• right click in your Python Terminal and choose Paste

world.set_block(pos, Item.IRON_BLOCK)
arms = pos + Direction.UP
world.set_block(arms, Item.IRON_BLOCK)
world.set_block(arms + Direction.EAST, Item.IRON_BLOCK)
world.set_block(arms + Direction.WEST, Item.IRON_BLOCK)
world.set_block(arms + Direction.UP, Item.CARVED_PUMPKIN)

Yay! You can paste again to create another one.

Say hello to the Iron Golem, your first Python creation!

(See “Creation” in this article https://minecraft.wiki/w/Iron_Golem if you don’t know about making iron golems)

How does this work? We use set_block to place all the necessary blocks in the world. We use the variables pos (which we set earlier) and arms to control where those blocks are placed.

Direction provides values that will move a position by one block in a particular direction when added/subtracted to/from that position. Note that we are using the operator + and that it can add more than just numbers.

So, first we place the golem’s feet at pos. Then we move UP one block from the position pos to the arm level of the golem and save that position in arms. Now we can step EAST and WEST from arms to make the arms. Finally we step UP to make the head.