Python Syntax, Indentation and Comments

Python Syntax Basics

Syntax means the grammar rules of a language. Python's syntax is famously clean: no semicolons, no curly braces for blocks. Instead, Python uses indentation (spaces at the start of a line) to group code.

Indentation — The Big Rule

In most languages { } mark a block. In Python, the indentation itself defines the block. Lines indented by the same amount belong together.

Comments

Comments are notes for humans; Python ignores them while running.

• Single-line: start with #
• Multi-line: wrap text in triple quotes """ ... """

Program 1: Indentation in Action

marks = 75

if marks >= 33:
    print("Pass")          # indented = inside the if
    print("Well done!")    # same block
print("Program over")      # not indented = outside the if

• The two indented lines run only when the condition is true.
• print("Program over") is not indented, so it always runs.

Program 2: Using Comments

# This program calculates the area of a rectangle
length = 10      # length in cm
width = 5        # width in cm

area = length * width   # formula: l x w
print("Area =", area, "sq cm")

The # notes explain the code without affecting output. Good comments explain why, not just what.

Program 3: Multi-line Strings as Notes

"""
Program: Greeting
Author : Student
Purpose: Print a welcome message
"""
print("Welcome to CodingEasily")

Triple-quoted text at the top is often used to describe a program or function (called a docstring).

Common Mistakes

• Inconsistent indentation (2 spaces here, 4 there).
• Mixing tabs and spaces.
• Forgetting the colon : before an indented block.

Practice Tasks

1. Write an if-block with two indented lines and one line outside it.
2. Add a comment above every line of a small program.
3. Add a 3-line docstring at the top of a program.

Summary

• Python uses indentation (4 spaces) instead of braces to group code.
• # makes a single-line comment; """ """ makes a multi-line one.
• A block always follows a colon :.