This tutorial is ideal for:
- Those who do Python as a part of GCSE Computer Science course- OCR, AQA and Edexcel
- Those who do Python as a part of AS/A Level Computer Science course - OCR, AQA and Edexcel
- A complete novice who wants to learn the nitty-gritty of computer programming
- Those who want a springboard for OOP - Object Oriented Programming
Python is an insanely simple programming language to learn, mimic real-life situations and develop high level applications in an elegant manner; it is a language loved by Google too. If you have a passion for programming, this tutorial is a springboard for reaching the ultimate goal, even if you are a complete beginner. If you are a seasoned programmer from another background, this is ideal for a new start.
First of all, here is the link to download the latest Python for a Windows PC: once installed, choose Python IDLE - Integrated DeveLopment Environment or Integrated Development and Learning Environment - from the programmes list. then, follow the instructions in the following animation to write your first piece of code and make it work. Please remember the code you see here will not be part of it!
You will see Python Shell Window, which looks like the following:
This is also called, interactive mode, because you can write Python commands here, run them by pressing the Enter key and see them at work on the same screen. For instance, in the above animation, I showed how to add, multiply and find the absolute value of a number by using Python commands. Python commands are written next to the primary prompt - >>>. The result is immediately shown just below the primary prompt.
In addition, you can open a Python file, write the commands in it, save it as a .py file and then execute it too - the more professional approach. The file thus saved, can be opened up later to amend the code and re-run it, which is as follows:
The first part of this tutorial is going to be in the interactive mode - the easier phase.
Programming in Interactive Mode
In interactive mode, Python shell can be turned into a versatile calculator, which is really fun! Here is how:
Let's, for instance, calculate the volume of a cylinder first:
Here are some examples for you to practise with the interpreter in the interactive mode - in order to be familiar with Python basic operators:
Variables - the containers in memory!
Variables store the information or data in the memory and act as containers. The type of container determines what it can store. The three main types of variables are:
- str - e.g. "Hello!", for string variables
- float - e.g. 21.34, for floating point numbers
- int - e.g. 3, for integers
In addition, there are a few other types: bool - e.g. true/false, Boolean.
In real life, if a sieve is a container, it cannot hold water, but it can hold ice. Exactly in the same way, an integer type cannot hold a string or vice versa. In short, the variable type does matter, when it comes to storing data.
The mechanism of a variable in programming is shown below:
As you can see, by knowing the exact data type, you can choose the right variable to store and manipulate it inside a programme.
The following animation shows how to determine the variable type by Python's built-in type()function:
In sieve-water analogy, water cannot be held in a sieve, but ice can be held if water can be turned into ice. In the same way, Python allows us to convert data from one type to another easily and then deal with them. In the following example, an integer is converted into a string and then back into an integer:
Note: the words followed by # is treated as a comment by Python; so, that part is not executed.
= means assignment, not equal in programming
The role of the equal sign, =, in programming is a confusing one for beginners. It is an assignment, as shown in the following code:
In short, = does not behave as the equal sign of an equation, that could lead to a bizarre outcome: a=a+6 => 0=6!
Mathematical Operations Involving Assignment(=)
Here are a few simple mathematical operations that could be done with the assignment sign:
The same can be performed with multiplication - * - and division - / - too.
In Python, strings can be manipulated to produce the desired outcomes. It is known as string concatenation.
In the above example, two words are assigned to the variables, a, and b. When the two variables are added, the string is concatenated to produce the combined phrase we want.
Those of us who use calculators know the use of functions quite well: for instance, in order to find the square root of a number, we use the button with the sign, √, to invoke the function that gives the square root of the number in question. The number that is entered into the function is called the parameter. The function is said to be returning the value of the number, when pressed. The simplified mechanism is as follows:
inner working hidden from the user
returning the square root as the output
The structure and the working of a function in Python is the same: we see the input and output, with the inner working being hidden from the user, unless you are a programmer. Here are some of the Python built-in functions at work:
A Python function to find the average of two numbers can be formed as follows:
In the above function, the def keyword defines the function and a and b are the parameters. The function returns the average of the two parameters, when entered into it; please note the indentation of the code, as it is really important in Python.
while loop: The following function shows how a while loop works;
The parameter, a, in the function accepts a number - the seed - and then print the number, increases it by 1 and stops working when the condition of the while is met.
for Loop: The following function shows the use of for loop:
In the first function, range(4) works from 0 to 3. In the second function, range(2,8) works from 2 to 7.
if loop: if loop is illustrated in the following function:
The above function shows how if loop works; please note how python check the equality with two equal signs.
More Advanced Functions
This is a fairly advanced function that checks whether the user input is odd or even with the aid of if loop.
Here is the full code for the above function:
if a%2 ==0:
print("It's an even number.")
print("It's an odd number.")
Graphics with Python turtle Library
In this case, we have to import a famous Python module called, turtle, which has been especially created for graphics. In order to use the
relevant functions, we have to make a reference to the library with the keyword, import, in the code.
Create the function, drawing_square(), inside Python shell as follows:
import turtle # importing the module
trtl = turtle.Turtle() #making a turtle object of Turtle class for drawing
screen=turtle.Screen() #making a canvas for drawing
screen.setup(400,300) #choosing the screen size
screen.bgcolor('black') #making canvas black
trtl.pencolor('red') #making colour of the pen red
trtl.pensize(5) #choosing the size of pen nib
trtl.speed(1) #choosing the speed of drawing
trtl.shape('turtle') #choosing the shape of pen nib
trtl.forward(100) #top line
#turn right through 900
trtl.forward(100) # right vertical line
trtl.forward(100) # bottom line
trtl.forward(100) # left vertical line
# information printing
# pause drawing
move the pointer to new position
trtl.pendown() # restart drawing
trtl.write('Square - Vivax Solutions', font=("Arial", 16, "bold"))
# the author informaton
trtl.ht() # draw a horizontal line
The above code, if properly run, produces the following image:
Fibonacci Sequence Generator
The following animation shows how to create a function to generate the famous Fibonacci Sequence in Python. The parameter, f, entered by the user, determines the size of the series.
The full code is as follows:
The following animation shows how to make a simple quadratic solver in Python:
THe complete code of the programme is as follows:
print ('No real solutions!')
print ('x = ' + str(e))
print ('x = ' + str(e) + ' or '+ str(f))
List is an amazing data type which can store a set of data, separated by commas.Here are two examples:
Cars =['Volvo','BMW','Ford','Citroen','Toyota']; Integers = [34,56,12,5,6,78]
The data in the list can be referred to by the index of each element: for instance, Cars='Volvo' and Integers=12.
Since list is a flexible data type, there are a few other ways to refer to the elements too. The animation shows most of them.
This tutorial is to be updated with object oriented approach soon. Last updated; 02 December 2016