April Python Bootcamp Day 5

 

Day 5: Conditional Statements in Python

Making Decisions in Your Code 

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 Introduction

In real life, we make decisions all the time:

• If it rains → take an umbrella
• If marks ≥ 90 → Grade A
• If balance is low → show warning

Similarly, in programming, we use conditional statements to control the flow of execution.

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 What are Conditional Statements?

Conditional statements allow a program to make decisions based on conditions.

They help programs:

• Execute different blocks of code
• Respond dynamically to input
• Implement logic like real-world systems

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 Core Idea

# if condition is True -> run code
# else -> skip or run something else

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 1. if Statement

 Syntax

if condition:
    # code block

 Example

age = 18

if age >= 18:
    print("You can vote")

 Runs only when condition is True

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 2. if-else Statement

Syntax

if condition:
    # True block
else:
    # False block

 Example

num = 5

if num % 2 == 0:
    print("Even")
else:
    print("Odd")

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 3. if-elif-else Statement

 Used when multiple conditions exist

 Syntax

if condition1:
    # block1
elif condition2:
    # block2
else:
    # default block

 Example

marks = 94

if marks >= 90:
    print("Grade A")
elif marks >= 75:
    print("Grade B")
elif marks >= 50:
    print("Grade C")
else:
    print("Fail")

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 Important Rule

 Only ONE block executes
 First True condition wins

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 4. Nested Conditions

 Condition inside another condition

 Example

age = 20
has_id = True

if age >= 18:
    if has_id:
        print("Entry Allowed")
    else:
        print("ID required")
else:
    print("Underage")

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 Important Concepts (Must Understand)

 Truthy & Falsy Values

if 0:
    print("Hello")
else:
    print("World")

 Output: World

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 Truth Table

• 0, None, False, "" → Falsy
• Everything else → Truthy

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 Order Matters

marks = 90

if marks >= 50:
    print("Pass")
elif marks >= 90:
    print("Topper")

 Output: Pass (because first condition matched)

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 Practice Problems

 Basic Level

1. Check whether a number is positive or negative.

1. Check whether a number is even or odd.

1. Find the greater number between two numbers.

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 Intermediate Level

4. Find the greatest among three numbers.

4. Check whether a given year is a leap year.

4. Create a grade system based on marks:

• 90 and above → Grade A

• 75 to 89 → Grade B

• 50 to 74 → Grade C

• Below 50 → Fail

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 Advanced Level

7. Check whether a given number is a palindrome.

7. Build logic for an ATM withdrawal system:

• Check if balance is sufficient

• Check if amount is a multiple of 100

7. Create a login system:

• Validate username and password

• Show success or error message