Python for Beginners: Write Your First Five Programs

Before you start: getting Python

Download Python 3 from python.org and install it. On Windows, tick the option to add Python to PATH during installation. Python installs with a simple editor called IDLE, which is enough for this guide. If you can't install software, an online Python editor works too.

Open IDLE, choose File → New File, type a program, save it with a name ending in .py, then press F5 to run it. The output appears in the shell window.

Program 1: Hello, world (output)

print("Hello, world!")
print("I am learning Python.")

print() displays whatever is inside the brackets. Text must be inside quotation marks; this kind of value is called a string. Each print() starts a new line.

Program 2: A personal greeting (variables and input)

name = input("What is your name? ")
print("Nice to meet you, " + name + "!")

A variable is a name that stores a value. Here, input() shows a question, waits for the user to type, and stores the answer in the variable name. The + sign joins strings together.

Program 3: Age next year (numbers)

age = int(input("How old are you? "))
next_year = age + 1
print("Next year you will be", next_year)

input() always gives back a string, even if the user types digits. int() converts it into a whole number so that arithmetic works. Passing several values to print(), separated by commas, prints them with spaces between them.

Program 4: Pass or fail (decisions with if)

score = int(input("Enter your test score (0-100): "))

if score >= 50:
    print("Pass")
else:
    print("Not yet a pass. Keep practising!")

if runs the indented lines only when its condition is true; else runs when it is false. The indentation (four spaces) is not decoration: in Python, it shows which lines belong to the if. Comparison operators include >=, <=, ==, !=, > and <.

Program 5: Times tables (loops and functions)

def times_table(number):
    for i in range(1, 11):
        print(number, "x", i, "=", number * i)

choice = int(input("Which times table? "))
times_table(choice)

def creates a function: a named, reusable block of code. number is a parameter, a value the function receives when it is called. The for loop repeats once for each value of i; range(1, 11) produces the numbers 1 to 10, because the end value is not included.

What to learn next

• Lists, which store several values in one variable.
• while loops, which repeat until a condition changes.
• Handling errors with try and except, so bad input doesn't crash your program.
• Small projects, such as a quiz, a number-guessing game or a simple calculator.

Short, regular practice works better than occasional long sessions. Change each example, predict what will happen before you run it, and then check whether you were right.