Create your own music using Python!

Posted on April 9, 2020 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges

For this challenge we will investigate how we can use Python code to create our own background music and sound effects to be used in a retro arcade game.

Most music editing software (e.g. GarageBand, Cubase, FL Studio, Logic Pro etc.), are Digital Audio Workstations (DAW) and let you create your own music by adding audio clips, virtual instruments and effects to a multi-track timeline. Editing and mixing your music is done through a Graphical User Interface.

On occasions, you may try a different approach to control the DAW through code. Websites such as EarSketch let you create your code online using either Python or JavaScript and import it to a DAW to visualise your timeline and play it.

Digitial Audio Workstation

In the example below, we are using Python code with basic audio clips from the “Eigthbit” library to recreate some retro arcade game music to be used on a game intro / splash screen.

It demonstrates some of the key basic features of EarSketch:

Set the tempo
Import audio clips (on different tracks and at specified times)
Add audio clips to the timeline
Add effects (including fade in, fade out and delay effects)
Use a loop to repeat a clip

Python Code

#		python code
#		script_name: Game_Intro.py
#
#		author: 101Computing
#		description: Background music for intro 
#

from earsketch import *

init()
setTempo(120)

clip1 = EIGHT_BIT_ATARI_SFX_004
clip2 = EIGHT_BIT_ATARI_LEAD_011
clip3 = EIGHT_BIT_ATARI_LEAD_010

pointA = 1.75
repeat = 3
pointD = pointA + repeat 

#fitMedia(Clip,Track,StartMeasure,EndMeasure)
fitMedia(clip1,1,1,2)
for i in range(0,repeat):
  fitMedia(clip2,2,pointA + i,pointA + i + 1)

fitMedia(clip3,3,pointA,pointD + 1)

#setEffect(Track,effect,parmeter,value)
setEffect(3, VOLUME, GAIN, -10)

#setEffect(Track,effect,parmeter,value,start measure,value,end measure)
#Fade in
setEffect(1, VOLUME, GAIN, -40, 1, 0, 1.75)
#Delay Effect
setEffect(1, DELAY, DELAY_TIME, 250)
setEffect(2, DELAY, DELAY_TIME, 250)
#Fade Out
setEffect(3, VOLUME, GAIN, -10, pointD, -60, pointD+1)

finish()

Test this code on EarSketch

You can test this code on EarSketch.

Test this script on EarSketch

Adding Background Music with PyGame

To add a background soundtrack, download a wav file or mp3 file into a folder called “Sounds”.

At the start of your code (main.py), after importing the pygame library, add the following lines of code:

pygame.mixer.pre_init(frequency=44100, size=-16, channels=2, buffer=4096)
pygame.mixer.music.load('Sounds/soundtrack.mp3')
pygame.mixer.music.play(-1) #-1 means loops for ever, 0 means play just once)

Note that you can stop the music at any time using the following instruction:

pygame.mixer.music.stop()

You may prefer to pause the music:

pygame.mixer.music.pause()

… or unpause the music:

pygame.mixer.music.unpause()

Adding Sound Effects using PyGame

To add sound effects, download some wav or mp3 files into a folder called “Sounds” and add the following code when you want to play the sound effect:

effect = pygame.mixer.Sound('Sounds/beep.wav')
effect.play()

Scratch -Take the Quiz!

Posted on March 29, 2020 by Administrator Posted in Block Programming, Coding Quiz, Computer Science, Computing Concepts, Quizzes, Scratch

Answer these 10 questions to test your understanding of Block Programming when using Scratch.

Take the Quiz! (open full screen)

Check that you understand the different types of validation checks by completing this quiz:

Extension Task

Use the scratch website to recreate some of the scripts used in this quiz.

Tagged with: Block Programming, Quiz, Scratch

Flowchart Prediction Tables

Posted on March 28, 2020 by Administrator Posted in Computer Science, Computing Concepts, GCSE Concepts, GCSE Quiz, Solved Challenges

For each of the following flowcharts complete the matching prediction table to work out the expected output based on the given input values.

Flowchart #1Flowchart #2Flowchart #3

Input Values		Expected Output
X	Y	Expected Output
10	15
8	6
16	12
10	5

Check my answers!

Input Values		Expected Output
X	Y	Expected Output
4	3
5	4
-5	3
0	10

Check my answers!

Input Values		Expected Output
X	Y	Expected Output
0	3
10	8
0	2
10	0

Check my answers!

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Computer Graphics Crossword

Posted on March 26, 2020 by Administrator Posted in Computer Science, Computing Concepts, Computing Terminology Quiz, Quizzes, Solved Challenges

Are you confident with your understanding of computer graphics? Can you explain the difference between bitmap graphics and vector-based graphics?

Computer GraphicsOpen Crossword Puzzle in a New Window

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Quiz

Bitmap vs. Vector Based Graphics

Posted on March 26, 2020 by Administrator Posted in Computer Science, Computing Concepts, Quizzes

It’s almost impossible to discuss graphics software without first establishing an understanding of the differences between the two major graphic types: bitmap and vector images.

The following “fill in the blank” activities will test your understanding of the characteristics of both types of graphics.

Bitmap/Raster GraphicsVector Based Graphics

Bitmap/Raster Graphics

pixels

Raster

(0,0,0)

million

tiny dots

resolution

PNG

Green

digital

8 mega pixels

(0,185,185)

scanner

Bitmap images (also known as images) are made up of in a grid. Pixels are picture elements; of individual colour that make up what you see on your screen. Pixels are defined by 2 properties: their position on the picture/grid and their colour value. These properties are stored in a bitmap file for every single pixel in the picture.

The colour value of each pixel is determined by the RGB colour code. (Red Blue). Each colour is made of a mix of these 3 primary colours. Each of these 3 colour have a value between 0 and 256. Hence a bitmap can have up to 256* 256 * 256 = 16 possible shades.

Red: (255, 0, 0)	Purple: (85,0,85)
Yellow: (255,255,0)	White: (255,255,255)
Cyan:	Black:

When you use a camera or a or a graphic tablet you create bitmap pictures.

Bitmap pictures come under different file extensions: BMP, GIF, JPEG, , TIFF.

The quality of a bitmap file is determined by its which tells you how many pixels the bitmap is made of. For instance a digital camera can have an resolution.

Pixel art graphics used in retro arcade games are a good example of bitmap pictures. You can create your own pixel art online using piskelapp.com

Vector Based Graphics

thickness

compressed

geometric shapes

processing

CAD drawings

grouped

pixelate

gallery

Vector Based graphics (also known as object-orientated graphics) are made up of many individual . Each of these shapes can be defined by mathematical/geometric statements and has individual properties assigned to it such as colour, fill, and size, , ...

All these geometric based data is saved in a vector based graphics as instructions such as:
DrawLine Red, 1 pixel wide, 10 pixels long From position x=20 y=40

When editing a vector based graphics each object can be edited individually. Objects can also be to be moved/resized/rotated together.

Cliparts from the clipart tend to be vector based. are also vector based.

Vector based graphics do not loose quality or pixelate when they are resized as opposed to bitmap graphics which do or become blurry when they are enlarged or resized. Vector based cannot be as opposed to bitmap files which can be compressed (by loosing some quality)

Vector based files tend to take up less disk space than bitmaps. However Vector based graphics requires more power to be displayed on the screen.

Create your own vector graphics online using vecteezy.com

Tagged with: Quiz

Data Validation Quiz

Posted on March 16, 2020 by Administrator Posted in A Level Concepts, A Level Quiz, Computer Science, Computing Concepts, Computing Terminology Quiz, GCSE Concepts, GCSE Quiz, Quizzes

When programming a computer system, it is good practice to include a range of validation checks in the code to check if the data being inputted by the end-user follows some basic rules.

The aim of validation checks is to ensure that data used or stored by computer systems is valid. Invalid data may indeed make the system crash or may provide inaccurate information back to the user.

Validation checks cannot confirm if the data is correct or not but they can filter out a lot of invalid data.

There are different types of checks that can be implemented in your code such as:

Presence Check: When a field has to be filled in (mandatory field) and cannot be left blank/empty. (e.g username field when you sign in to a new system)
Length Check: When a field has to contain a set number of characters (e.g. a password is at least 8 characters long, a credit card number contains 16 digits).
Type Check: When a field has be of a certain data type (integer, float/real, etc.).
Range Check: When a field has be within a range, or greater or lower than given value. (e.g. A percentage value has to be between 0 and 100)
Lookup Check: When a field can only accept a certain set of values from a list (e.g. A title field can be either Mr, Mrs, Ms or Dr)
Character Check: When a field has to contain a specific character or type of characters. (e.g. An e-mail address should contain an “@” sign)

Take the Quiz! (open full screen)

Check that you understand the different types of validation checks by completing this quiz:

Tagged with: Quiz

Vera Molnár’s Artwork revisited using Python

Posted on March 14, 2020 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges

Vera Molnár (born 1924) is a French media artist of Hungarian origin. She is considered to be a pioneer of computer art. Trained as a traditional artist, she began working with computers in 1968, where she began to create algorithmic paintings based on simple geometric shapes and geometrical themes.

In this blog post we are looking at using Python Turtle to recreate some of her artwork. To create you own op art/computer art, you will need to be confident in using iterative algorithms and have a good understanding of Cartesian coordinates.

To find review some of Vera Molnár’s artwork you can use the following pages:

Artwork #1

This is our first attempt at recreating some of Vera Molnár’s artwork using Python Turtle.

Artwork #2

This is our second attempt at recreating some of Vera Molnár’s artwork using Python Turtle.

Your Task

Your task is to select on other piece of artwork from Vera Molnár and write a computer algorithm using Python Turtle to recreate it. You can do so by adapting the scripts provided above.

Find more work from Vera Molnár on Google Images

Tagged with: Computer Art, Coordinates, iteration, Python Turtle

Triangle Geometry Functions

Posted on March 8, 2020 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

In this challenge we will create a library of functions to apply the different formulas based on the geometry of triangles.

For each function, you will need to design the algorithm using either Pseudo-code or a flowchart, implement the function using the Python trinket provided below and use another algorithm to test your function.

PerimeterAreaAnglesEquilateralIsoscelesPythagoras' TheoremHeron's Formula

Write a function called getPerimeter() that takes three parameters/arguments a, b, c (the length of each side of a triangle).

Your function should calculate and return the perimeter of this triangle.

Write an algorithm to test your function.
Your algorithm should:

Ask the user to enter the length of the 3 sides of a triangle,
Use the getPerimeter() function to retrieve the perimeter of the triangle,
Display the perimeter of the triangle

Write a function called getArea() that takes two parameters/arguments corresponding to the length of the base and of the height of a triangle.

Your function should calculate and return the area of this triangle.

Write an algorithm to test your function.
Your algorithm should:

Ask the user to enter the length of the base and height of a triangle,
Use the getArea() function to retrieve the area of the triangle,
Display the area of the triangle

Write a function called getAngle() that takes two parameters/arguments called angle1 and angle2 (the value of two angles in degrees)

Your function should calculate and return the value of the third angle: (180 – angle1 – angle2)

Write an algorithm to test your function.
Your algorithm should:

Ask the user to enter the value of two angles in degrees,
Use the getAngle() function to retrieve the value of the third angle,
Display this value on screen.

Write a function called isEquilateral() that takes three parameters a, b, c (the length of each side of a triangle).

Your function should workout if the triangle is equilateral (if all sides have the same length) and return a Boolean value (True or False) based on its finding.

Write an algorithm to test your function.
Your algorithm should:

Ask the user to enter the length of the 3 sides of a triangle,
Use the isEquilateral() function to find out if the triangle is an equilateral triangle,
Display a relevant message to the end user.

Write a function called isIsoscles() that takes three parameters a, b, c (the length of each side of a triangle).

Your function should workout if the triangle is an isosceles triangle (if any two sides have the same length) and return a Boolean value (True or False) based on its finding.

Write an algorithm to test your function.
Your algorithm should:

Ask the user to enter the length of the 3 sides of a triangle,
Use the isIsoscles() function to find out if the triangle is an isosceles triangle,
Display a relevant message to the end user.

Write a function called getHypotenuse() that takes two parameters/arguments called a and b (the length of two sides of a right-angled triangle).

Your function should calculate and return the length of the third side (the hypotenuse) of the triangle knowing that:
triangle-pythagoras-formula

Write an algorithm to test your function. Your algorithm should:

Ask the user to enter the length of the 2 sides of a right-angled triangle,
Use the getyHypotenuse() function to retrieve the value of the hypotenuse of the right–angled triangle,
Display the value of the Hypotenuse.

Write a function called isRightAngledTriangle(), that takes three parameters a, b and c and works out if the triangle is a right-angled triangle or not. Your function should return a Boolean value (True or False) based on its finding.

Write an algorithm to test your function. Your algorithm should:

Ask the user to enter the length of the 3 sides of a triangle,
Use the isRightAngledTriangle() function to find out if the triangle is a right-angled trinagle,
Display a relevant message to the end-user.

Write a function called getTriangleArea() that takes three parameters/arguments a, b, c (the length of each side of a triangle).

Your function will apply Heron’s formula to calculate and return the area of the triangle.

Write an algorithm to test your function.
Your algorithm should:

Ask the user to enter the length of the 3 sides of a triangle,
Use the getTriangleArea() function to retrieve the area of the triangle,
Display the area of the triangle

Python Code

We have already started the code for you and have completed the function getPerimeter() followed by a short algorithm to test this function.

Your task is to complete this Python script to create and test all the functions mentioned above.

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Function, subroutines

Heron’s Formula

Posted on March 3, 2020 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges

The Heron’s formula is a famous formula used to calculate the area of a triangle based on the length of its three sides. It is called “Heron’s Formula” (sometimes called Hero’s formula) after Hero of Alexandria who was a Greek Engineer and Mathematician in 10 – 70 AD.

Python Task

Your task is to write a function called calculateTriangleArea(). Your function will:

Take three parameters corresponding to the length of the 3 sides of a triangle: a, b and c,
Apply Heron’s formula to calculate the area of the triangle,
Return the area of the triangle.

You will also then need to create a small program that will:

Ask the user to enter the length of the three sides of a triangle,
Calculate the area of the triangle using the calculateTriangleArea() function,
Output the area of the triangle.

Video Tutorial

Python Code

Test Plan:

Once your code is done, complete the following tests to check it is working as expected:

Test #	Input Values (in cm)	Expected Output (in cm²)	Pass/Fail?
#1	First side: 3 Second side: 4 Third side: 5	Area: 6
#2	First side: 8 Second side: 10 Third side: 12	Area: 39.686
#3	First side: 4 Second side: 8 Third side: 10	Area: 15.199

Extension Task #1

Create some extra functions to calculate the area of a square, of a rectangle and of a disc. Each function will need to accept the relevant parameters needed to calculate the area of the desired shape.

Extension Task #2

Create a menu system, where the user is asked what shapes they would like to calculate the area of before being asked to enter the relevant dimensions.

Did you know?

Illustration of Hero’s Aeolipile (Steam Engine)

Hero published a well-recognized description of a steam-powered device called an aeolipile (sometimes called a “Hero engine”). Among his most famous inventions was a windwheel, constituting the earliest instance of wind harnessing on land.

Tagged with: Function

Linear Search Functions

Posted on February 27, 2020 by Administrator Posted in Algorithms, Algorithms (GCSE), Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

For this programming challenge we will investigate different functions which will all be based on a linear search algorithm.

Let’s consider a teacher who has decided to keep track of rewards issued to their students throughout the term by adding their name at the end of a text file each time they win a reward for their positive attitude and effort in lessons.

The teacher would like to write a few Python functions to:

scan the content of the text file and check if a particular students has received a reward or not,
count the number rewards a student has received throughout the term.
locate a student in the text file (identify the position/line number where the student’s name appear in the text file)

The teacher has started the code by creating a function called readTextFile() that takes a parameter called filename/ This function scan the context of the text file and return a list of all the names listed in the text file.

Using flowcharts, the teacher then worked out the algorithms for the extra functions they would like you to implement and test to complete the code. You can access these flowcharts below.

Is Listed?Rewards CountFind Position

The first function that you will need to implement is called isListed(), takes two parameters value and list and returns True if the value can be found in the list, false otherwise. To test this function you will need to implement the following algorithms:

Click on the above flowcharts to open in a new window

The third function is called count(), takes two parameters value and list and returns number of times the searched value appears in the list. To test this function you will need to implement the following algorithms used to count the number of rewards a student has received throughout the term.

Click on the above flowcharts to open in a new window

The second function to implement is called findPosition() takes two parameters value and list and returns the position (starting at position 1) of the value in the list or -1 if the item is not found. To test this function you will need to implement the following algorithms used to locate a name in the text file by identifying the line number where such name appears in the file.

Click on the above flowcharts to open in a new window

Python Code

You can now complete and test all three functions using the flowcharts provided above. The trinket below contains two tabs. In the second tab called “rewards.txt” you can access the content of the text file.

Alternative Approach

The Python syntax allows you to use loop through a list of values as follows:

for value in list:
   print(value)

Not all programming languages will let you use this syntax. An alternative approach is to use indices:

for i in range(0,len(list)):
   print(list[i])

In this case the flowchart for our count() function would become:

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Flowchart, Function, subroutine

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Python Code

Test this code on EarSketch

Adding Background Music with PyGame

Adding Sound Effects using PyGame

Take the Quiz! (open full screen)

Extension Task

Solution...

Solution...

Bitmap/Raster Graphics

Vector Based Graphics

Take the Quiz! (open full screen)

Artwork #1

Artwork #2

Your Task

Python Code

Solution...

Python Task

Video Tutorial

Python Code

Test Plan:

Extension Task #1

Extension Task #2

Did you know?

Python Code

Alternative Approach

Solution...

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