Category: Software Design & Devlopment

Python on Raspberry Pi

For a bit of a change the class were programming in Python on a Raspberry Pi.

The program below was used to create a Gold Block in Minecraft.

1
2
3
4
5
6
7
8
 
from mcpi . minecraft import Minecraft
import mcpi . block as block
mc = Minecraft . create ()
pos = mc. player . getPos ()
x = pos.x
y = pos.y
z = pos.z
mc. setBlock (x, y, z, block . GOLD_BLOCK .id)

Created using http://hilite.me/ and http://www.geocraft.org.uk/

Array Handling

In Python array handling can be accomplished by using Python’s built in list comprehension. This means when we are working with arrays we need to change the way we use the for loop depending on whether we are interested in the value or the position of the value.

list

In the code above the first for loop is simply printing the value from the list. The second loop knows the position of each item and can therefore display that information as well.

Incrementing Counter

This is a programming statement which increases by a known amount, each time it is called.

  • Score=Score+1
  • One=One+1
  • Bonus=Bonus+10

Incrementing counters are often used inside loops to keep track of the number of iterations.

counter

In the example above the tries=tries+1 line is keeping track of how many times the loop has been iterated.

Python Selection – if:

diceToday we investigated the use of the if statement, this is a selection statement which allows Python to make choices.

We have updated our dice roll program from last time to include a for loop and multiple if statements. The program now displays a summary of the results of 1000 dice rolls.

For homework the class were asked to TRACS the program and we will discuss how efficient it is next time.

Python Functions

A function is a predefined block of code which is used then programming. It often contains a number of commands and steps.

Here are some of the functions we have met

print()

This function displays the string that is contained in it parenthesis ().

print(‘Hi there, how are you?)

input()

This function displays the string in its parenthesis but allows the user to enter a string that is then returned and assigned to a variable.

age=input(‘What is your age?’)

str()

Converts the contents of its parenthesis to a string

check=input(‘Is your age ‘+str(age))

len()

Outputs the length (number of characters) of a string or the size (number of elements) in an array

print(‘The length of your name is’,len(name))

float()

Converts a value to a floating point number

weight=float(input(‘How many KG do you weight’))

int()

Converts a value to an integer

age=int(input(‘What is your age?’))

 

Import Function

Python is a general purpose language which means that it can be used to solve many different tasks. However Python does not have a command for every single eventuality. So programmers have created document with lots of different functions, these are called module libraries.

The import command is used to import module libraries into python programs.

dice

The random module stores a number of functions, to get access to the function we want we must first import random then use dot notation to specify the function we want to call. So random.randint calls the randint function from the random module library we imported previously.

There are libraries to do many things and they all should come with documentation to make them easy to use. Like all python programs they are open source so you can have a look inside to see how they work. Here are some example