🐍 Python Basics: Modes, Variables & Comments
Interactive Mode, Script Mode, Error Correction, and Variables
📚 About this guide: Complete, exam-friendly notes for learning Python Programming Basics. Master the difference between Interactive and Script modes, learn how to fix errors, add comments, and use variables with the
print() statement.
Concept 1
What is Interactive Mode?
When you launch Python IDLE, you see the Python Shell with the >>> prompt. This is Interactive Mode, which allows individual Python commands to be typed directly and carried out immediately.
>>> print("Hello world")
Hello world
>>> (7+6)*2
26
>>>
⚠️ Important: Python is case-sensitive. You must type commands using lower-case letters (e.g.,
print, not Print). Also, you do not need the print command for basic calculations in the shell.
Keywords
Essential Vocabulary
- Interactive mode: The Python shell allows commands to be entered and run immediately.
- Python shell: The interactive mode environment where commands are typed directly.
- Print statement: A Python command used to output text or values onto the screen.
- Case sensitive: Able to distinguish between capital and small letters.
- Interpreter: Translates Python code into machine code line by line.
- Machine code: The binary language a computer uses to carry out instructions.
Practice
Interactive Mode Practice Tasks
- Enter:
print("Welcome to the Python Shell") - Enter a command to print your name:
print("Your Name") - Fix the error:
print("Hello World)(Missing closing quotation mark). - Fix the calculation:
(7+3*2is missing a bracket. Correct it to(7+3)*2to get 20. - Try four of your own math commands (remember
*is for multiplication). - Get Python to add 150 and 23, then multiply by 3:
(150 + 23) * 3
Concept 2
What is Script Mode?
In Interactive Mode, code cannot be saved. Script Mode uses a text editor (like Notepad) to write, save, and run multiple lines of code as a complete program.
Steps to Create & Run:
- Create: In the Python shell, select File → New File.
- Type: Enter your code (e.g.,
print("Hello world")). - Save: Select File → Save As. Name it
HelloWorld.py(the.pyextension is required). - Run: Select Run → Run Module (or press F5). The output appears in the Shell window.
Concept 3
Correcting Errors in Script Mode
If there is an error, Python highlights it in red and provides an error message.
Print("Hello World")
# Error: NameError: name 'Print' is not defined
How to fix: Open the program, correct the mistake (change Print to print), save, and run again.
Concept 4
Adding Comments
Comments explain what the code does. The Python interpreter ignores them. Start a comment with a hash (#) symbol.
# This is an Adventure Game about The Digital Sweet Shop
# The program was written by me
print("Welcome to The Digital Sweet Shop")
print() # This prints a blank line
Keywords
Script Mode Vocabulary
- Script mode: Python's text editor, allowing programmers to enter a list of commands executed together.
- Execute: Another word for running a program.
- Comments: Text entered by a programmer to improve code readability; starts with
#in Python.
Practice
Hands-On Practice Tasks
- Create a New File in IDLE.
- Type:
print("Welcome to my first program in Python") - Add a line to print your favourite hobby.
- Save as
My First Program.pyand Run (F5). - Add these lines:
print("Did you know Python can do calculations? The line below displays 10") print(7+3) print("How about this? The calculation below should display 25") print(7+3*2+5) - Fix the error: The last line outputs 18, not 25. Correct it to
print((7+3)*2+5)and add a#comment above it explaining the BIDMAS/PEMDAS fix. - New Program: Create
Maths Favourites.pythat prints your name, favourite number, and favourite calculation (e.g., "Name: Adnan", "Favourite number: 7", "Favourite calculation: multiplication").
Concept 5
What is a Variable?
A variable is a named location in the computer's memory that stores data of a particular type. Data can be assigned directly in the code or from user input.
name = "Ardeel"
age = 12
address = "Station Road"
colour = "Red"
Concept 6
Printing with Variables
To print a variable alongside text, do not put the variable name in quotation marks. Use a comma to join the text and the variable.
print(name)
# Output: Ardeel
print("Your name is", name)
# Output: Your name is Ardeel
print("Your name is", name, ". Nice to meet you.")
# Output: Your name is Ardeel . Nice to meet you.
🔑 Keyword:
- Variable: A named memory location used to store data of a given type during program execution; a variable can change value as the program runs.
Practice
Variable Practice Tasks
- Create a new file and type:
name = "Ardeel" age = 12 address = "Station Road" colour = "Red" print("Your name is", name) - Add code to display the age:
print("You are", age, "years old") - Complete the program to say:
print("You live at", address) - Complete the program to say:
print(colour, "is your favourite colour") - Final Task: Create a new program showing your name, age, address, and favourite colour. Save and run it.
❓ Frequently Asked Questions (FAQ)
Q: What is the difference between Python Interactive Mode and Script Mode?
A: Interactive Mode (Python Shell) allows you to type and execute single lines of code immediately, but they cannot be saved. Script Mode uses a text editor to write, save (.py), and run multiple lines of code as a complete program.
Q: What is a variable in Python?
A: A variable is a named location in the computer's memory used to store data of a particular type. Variables can change their value as the program runs.
Q: How do you add comments in Python?
A: In Python, you add comments by starting a line with a hash (#) symbol. The Python interpreter ignores any text on a line after the # symbol, making it useful for explaining code.
Q: Why is Python considered case-sensitive?
A: Python is case-sensitive, meaning it distinguishes between uppercase and lowercase letters. For example, 'print' is a valid command, but 'Print' will cause a NameError.
