Exercise 04

Spawning a line of blocks - While Loop - Modulo

Spawning a line of blocks - using a while loop - playing with modulo

Note : We already saw the “setBlocks” function in Exercice 3. It allows line creation in an easier (yet less modular) way *

The while construct consists of a block of code and a condition/expression. The condition/expression is evaluated, and if the condition/expression is true, the code within the block is executed. This repeats until the condition/expression becomes false. Because the while loop checks the condition/expression before the block is executed, the control structure is often also known as a pre-test loop. Compare this with the do while loop, which tests the condition/expression after the loop has executed. ¹

First let’s create a line made of say 10 blocks of Spruce Wood Plank (id : 5:1)

import mcpi.minecraft as minecraft
import mcpi.block as block
mc = minecraft.Minecraft()

#Here we get the player position
x,y,z = mc.player.getPos()

#We will set the number of blocks we want in a variable
size = 10
#We will use a counter to store the number we already built.
counter = 0

#And here is the while loop. 
while counter < size:
#We create our block and at each iteration we will set new one next to previous one
  mc.setBlock(x+counter,y,z,5,1)
#We need to increment our counter each time we set a block to get the expected result
  counter = counter+1
#The Loop will stop when counter will be equal to size

And here is what you should get : 10 blocks line of Spruce Wood Plank

You can play with size to see this line growing. We can also play with the subid of the wood at each iteration using a modulo.

In computing, the modulo operation finds the remainder after division of one number by another (sometimes called modulus). ²

So for instance for modulo 6

Source	0	1	2	3	4	5	6	7	8	9	10	11	12	13	etc.
Modulo 6	0	1	2	3	4	5	0	1	2	3	4	5	0	1	etc.

We’ll use this to alternate on the kind of wood. 5 modulo 6 in python will be written 5 % 6

import mcpi.minecraft as minecraft
import mcpi.block as block
mc = minecraft.Minecraft()

#Here we get the player position
x,y,z = mc.player.getPos()

#We will set the number of blocks we want in a variable
size = 10
#We will use a counter to store the number we already built.
counter = 0

#And here is the while loop. 
while counter < size:
#We create our block and at each iteration we will set new one next to previous one and the kind of wood will move to next subid
  mc.setBlock(x+counter,y,z,5,counter%6)
#We need to increment our counter each time we set a block to get the expected result
  counter = counter+1
#The Loop will stop when counter will be equal to size

You should get something like: 10 blocks line of alternating Wood Plank

We can do the same with Wool (35) and a module 16 (as there are 16 color of wool). We’ll also make a diagonal playing with the z coordinate as well

import mcpi.minecraft as minecraft
import mcpi.block as block
mc = minecraft.Minecraft()

#Here we get the player position
x,y,z = mc.player.getPos()

#We will set the number of blocks we want in a variable
size = 32
#We will use a counter to store the number we already built.
counter = 0

#And here is the while loop. 
while counter < size:
#We create our block and at each iteration we will move x and z from 1 so we'll get a diagonal
  mc.setBlock(x+counter,y,z+counter,35,counter%16)
#We need to increment our counter each time we set a block to get the expected result
  counter = counter+1
#The Loop will stop when counter will be equal to size

And voila ! 32 blocks diagonal line of wool alternating colors 04-line-diag-wool.png

While Loop ↩
Modulo ↩

2016-11-19 exercises
exercises