AOS1: Programming

On completion of this unit the student should be able to design working modules in response to solution requirements, and use a programming or scripting language to develop the modules

We will be using Grok Learning as the main lesson sequence in learning the programming language Python. This will be extended with examples using Easygui and the Python Image Library

Python is the most popular language for 1st year university courses, for data science and machine learning (artificial intelligence). It is also running the back-end of many of the larger websites on the internet. It is a good first language to learn and has a lot of utility. Python is also Free software (i.e., costs no money and is open source) and the primary implementation is available at Python.org

Key Knowledge

Data and information

characteristics of data types and methods of representing and storing text, sound and images

Digital systems

functions and capabilities of key hardware and software components of digital systems required for processing, storing and communicating data and information

Approaches to problem solving

functional requirements of solutions
methods for creating algorithms such as identifying the required output, the input needed to produce the output, and the processing steps necessary to achieve the transformation from a design to a solution
suitable methods of representing solution designs such as data dictionaries, data structure diagrams, object descriptions and pseudocode
characteristics of effective user interfaces, for example useability, accessibility, structure, visibility, legibility, consistency, tolerance, affordance
techniques for manipulating data and information
naming conventions for files and objects
testing and debugging techniques, including construction of test data

Key skills

interpret solution requirements
select and use appropriate methods for expressing solution designs, including user interfaces
apply techniques for manipulating data and information using a programming or scripting language
devise meaningful naming conventions for files and objects
apply testing techniques using appropriate test data

Student Activities

Research the CPUs & GPUs of a mobile phone, a laptop and a desktop gaming machine. How do they differ and how is their performance measured?
Research three popular languages to discover their origins. What did existing languages lack that led to the need for the new languages?
Exercises in Grok Learning's Intro to Programming in Python 1 & 2
Class activities including Easygui interface
- Guess my number game
- Login Module (no password hashing)
- ROT13 & Whitespace encoder (ASCII)
PIL Examples with optional easygui interface (RBG Bitmaps)
- Add white stripes over an image
- Reflect Image around x or y axis or line x=y
- Rotate image by 90°
- Grayscale / Colour shift image
- Extensions:
  - Droste Effect [Original, Footscray]
  - Fractals (E.g., Mandelbrot & friends)

Resources

Grok Learning (Your teacher will add you to a class)
We'll be using Python version 3.6. Available from Python.org.
Visualize Python - A really good way to view the execution of (simple) Python programs
trinket is a Skulpt based service
Installing easygui and Pillow on the School machines
Official Easygui tutorial
Official Pillow tutorial

Code Snippets - Easygui

>>> import easygui

>>> easygui.egdemo() # opens menu to demo all functionality

Easygui allows for easy sequential input and output (just like the text-based programs using input and print statements)

>>> import easygui

>>> name = easygui.enterbox(msg='What is your name?',

                            title='Hi there!')

>>> easygui.msgbox(msg='Nice to meet you, {}'.format(name))

'OK'

Code Snippets - PIL

Notes:

Will mainly use BMP or PNG files, to avoid lossy compression issues
We will use the .load() method to get pixel array, faster than using .getpixel for each pixel. Grok's image manipulation course uses the latter method, but is still a good resource.

Basic pixel-level image manipulation example on the old-old FCC logo

from PIL import Image

# Basic example showing how to open a file

# Read properties of image, Read & write pixels, Save

# Open an image in same directory as Python script

img = Image.open("FCC.png")

# Print some properties of the image

print(img.filename, img.size, img.mode)

# Display image using default image viewer of OS

img.show()

# Access a 2D pixel array for the image

pix = img.load()

# Read of a pixel near the middle

print(pix[100, 60])

# Set a block of pixels near the middle white

pix[100, 60] = (255, 255, 255)

pix[101, 60] = (255, 255, 255)

pix[100, 61] = (255, 255, 255)

pix[101, 61] = (255, 255, 255)

img.show()

# Loop over ALL pixels

# Set every second horizontal line grey

for x in range(img.size[0]):

    for y in range(img.size[1]):

        if y % 2 == 0:

            pix[x, y] = (127, 127, 127)

img.show()

# Save changes to a new file

new_filename = img.filename[:-4]

             + "stripy"

             + img.filename[-4:]

img.save(new_filename)

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