Getting Started With Python Brendan Routledge

What is Python? A widely-used programming language Focus is on code readability and syntax allows concepts to be expressed in fewer lines of code Python is used by many major organisations including NASA and YouTube It is one of the 3 programming languages which can be used to write Google Apps

The Computing Curriculum At Key Stage 1 children will understand algorithms, that programmes require precise instructions, will create and debug simple programmes, predicting how they will work and understand how technology appears in everyday life At Key Stage 2 children will design, write and debug programs, use sequence, selection, and repetition in programs, work with variables and different kinds of input, be able to correct errors in programmes and algorithms and understand how networks work At Key Stage 3 learners will understand use of key algorithms that reflect computational thinking, use 2 or more programming languages, one of which is textual, design and develop modular programs that use procedures or functions, understand simple Boolean logic and some of its uses in circuits and programming

Key Aspects What is an Algorithm? The need for Precision The importance of Prediction Essential skills of Debugging Importance of Sequencing Efficiency of Repetition/Looping Use of Variables to extend functionality

The Iterative Process of Programming PLAN Plan how your program will solve the problem PROGRAM Use your plan to write/edit your program TEST Does your program do what you wanted? DEBUG Fix any problems and improve it ANALYSE What is the problem you need to solve?

Working within the Python Shell Select ‘Idle’ to open the editor/interpreter This editor is an area to try out commands – what you write here is not saved! Try these – do they work?: print(5) Print(5) print(hello) print(‘hello world’) print(“hello world”) So ‘print’ means output something to the screen

Working within the Python Shell print(“Question: What goes clip?\nAnswer: A one legged horse”) Try this: print(“Question: What goes clip?”) then print(“A one legged horse”) then try Escape sequences are specific switches to change the way things display \n creates a return line in a string of text \t creates a tab indent in string of text \\ allows a backslash to appear in string of text \” allows speech mark to appear in string of text

Working within the Python Shell Try these – do they work?: input() input(What is your name?) input(“What is your name?”) input(‘What is your name?’) So ‘input’ means input something from keyboard

Working with variables A variable is a container which stores some data for use later or elsewhere. A variable needs a name so that it can be identified when it is used. Call your variable ‘a’ and give it a value a = 5 Ask Python what ‘a’ is by typing ‘a’ and it will return a value Variables can also be text strings – a = “hello world” So a variable is a way of storing data for use in a program

Working with variables Variables need more suitable names to identify them. myName = “Brendan” faveFood = “Fish ” type ‘myName’ – does it output the expected value of the variable? Variables should be carefully named when used in your program

Python for Maths Can use Python as a mathematical tool. Try typing Use + - * / Make this into a variable sum = Try some other calculations Python can carry out many mathematical operations

Using repetition To use repeated commands (loops) in Python is easy. number=1 while number < 101: print (number) number = number+1 Task – write a short program which counts up to 100 in 5s Python handles repetition and looping easily Was your program: number=0 while number < 101: print(number) number = number+5

Using repetition Try creating a text string which loops lines=0 while lines < 50: print (“I will not write code in Art lessons”) lines = lines+1 Try some of your own ideas Python handles repetition and looping easily

Creating and saving a program From Python Shell window, select File > New File to open new window Save your program with a new filename Write a very short program e.g. print(“Hello this is my very first program in Python”) then run it by pressing F5. Write a simple function, as follows: Start with a comment – denoted by a # at the start of the line Script could be something like: # This program will say hello to the user def main(): print(“What is your name?”) yourName = input() print(yourName) Run program – at the prompt type main()

Creating and saving a longer program From Python Shell window, select File > New File to open new window Save your program with a new filename Write a short programme which defines a function called times_tables and which allows you to see any times table. Start with: def times_tables(num): n=1 while n <= 10: print(n, "x", num, "=", n*num) n =n+1 How would you make it display a different partof a times table, say from 20 to 30?

An even longer program…. We are going to make a Number Guessing Game. Computer will think of a number and player will try to guess it Copy the code from the sheet very carefully. As you go try to figure out what each bit of the code does in the game Two new things in this script: 1.The ‘return’ keyword – tells the is_same() function what value should be sent back when it is called. As well as sending data to functions they can also return data. Here it returns the value of the variable result 2. Converting user’s input into an integer – this is done by wrapping it in int(input……). This is because anything coming from keyboard input is received as strings. So it has to be converted to a different type of data – this is called casting.

Some useful Python resources Python Scheme of Work for Upper KS2 Coding at School Python Programming Guide – Simon Haughton Python Tutorial for Schools Coding Club Learn Street