Conditional Statements in Python 🚦

Conditional statements in Python allow your program to make decisions based on specific conditions. Here’s a comprehensive overview:

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1. if Statement ✅

Executes a block of code only if a condition is True.

Python

age = 18
if age >= 18:
    print("You are eligible to vote")

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2. if-else Statement ❓

Adds an alternative path when the if condition is False.

Python

temperature = 30
if temperature > 25:
    print("It's hot outside")
else:
    print("It's cool outside")

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3. if-elif-else Statement 🪜

Handles multiple conditions sequentially. The first true condition executes its block.

Python

score = 85
if score >= 90:
    grade = 'A'
elif score >= 80:
    grade = 'B'  # This block executes
elif score >= 70:
    grade = 'C'
else:
    grade = 'F'
print(f"Your grade is {grade}")  # Output: B

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4. Nested Conditionals 🧩

if statements inside other if statements.

Python

num = 10
if num > 0:
    if num % 2 == 0:
        print("Positive even number")
    else:
        print("Positive odd number")
else:
    print("Non-positive number")

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5. Ternary Operator ❓➡️

A concise one-line expression for simple if-else logic.

Python

is_rainy = True
activity = "Stay indoors" if is_rainy else "Go hiking"
print(activity)  # Output: Stay indoors

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6. Logical Operators (and, or, not) 🤝

Combine multiple conditions:

Python

age = 25
has_license = True
if age >= 18 and has_license:
    print("You can drive")  # Executes

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7. Truthiness Checks 💡

Non-boolean values are evaluated as True (non-zero, non-empty) or False (zero, empty, None).

Python

name = ""
if not name:  # Checks if name is empty
    print("Name is required")

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Key Rules: 📜

• Colon and Indentation: Always end conditions with : and indent code blocks. ➡️Pythonif condition: # Colon required ... # Indentation (4 spaces)
• Execution Flow: Conditions are checked top-to-bottom. The first true condition triggers its block and exits the structure. ⬇️
• else is Optional: Use when you need a default action. 🤷
• Parentheses: Optional for simple conditions but improve readability for complex logic. ()Pythonif (age > 12) and (age < 20): print("Teenager")

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Example: User Authentication 🔒

Python

username = "admin"
password = "secret123"

if username == "admin" and password == "secret123":
    print("Access granted")
elif username == "admin":
    print("Wrong password")
else:
    print("Invalid username")

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Common Use Cases: 🎯

• Validating user input ✅
• Controlling program flow ➡️
• Error handling 🛡️
• Feature toggling based on conditions 💡

1. Number Sign Checker

Checks if a number is positive, negative, or zero.

python

num = float(input("Enter a number: "))
if num > 0:
    print("Positive number")
elif num < 0:
    print("Negative number")
else:
    print("Zero")

2. Voting Eligibility

Determines if a person is eligible to vote.

python

age = int(input("Enter your age: "))
if age >= 18:
    print("You can vote!")
else:
    years_left = 18 - age
    print(f"Wait {years_left} more year(s) to vote")

3. Leap Year Checker

Checks if a year is a leap year.

python

year = int(input("Enter year: "))
if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0):
    print(f"{year} is a leap year")
else:
    print(f"{year} is not a leap year")

4. Simple Calculator

Performs basic arithmetic operations.

python

num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))
operation = input("Choose operation (+, -, *, /): ")

if operation == '+':
    result = num1 + num2
elif operation == '-':
    result = num1 - num2
elif operation == '*':
    result = num1 * num2
elif operation == '/':
    result = num1 / num2 if num2 != 0 else "Error! Division by zero"
else:
    result = "Invalid operation"

print(f"Result: {result}")

Conditional Statement Examples 🚦

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1. Vowel or Consonant Checker 🗣️

Checks if a character is a vowel or consonant:

Python

char = input("Enter a character: ").lower()
if char in 'aeiou':
    print(f"{char} is a vowel")
elif char.isalpha():
    print(f"{char} is a consonant")
else:
    print("Invalid input - please enter an alphabet character")

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2. Discounted Bill Calculator 💸

Applies discounts based on purchase amount:

Python

amount = float(input("Enter purchase amount: $"))
if amount > 1000:
    discount = 0.20
elif amount > 500:
    discount = 0.15
elif amount > 200:
    discount = 0.10
else:
    discount = 0

final_amount = amount - (amount * discount)
print(f"Discount: {discount*100}% | Final amount: ${final_amount:.2f}")

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3. Month Number to Name Converter 📅

Converts month number to month name:

Python

month_num = int(input("Enter month number (1-12): "))
if month_num == 1:
    print("January")
elif month_num == 2:
    print("February")
elif month_num == 3:
    print("March")
elif month_num == 4:
    print("April")
elif month_num == 5:
    print("May")
elif month_num == 6:
    print("June")
elif month_num == 7:
    print("July")
elif month_num == 8:
    print("August")
elif month_num == 9:
    print("September")
elif month_num == 10:
    print("October")
elif month_num == 11:
    print("November")
elif month_num == 12:
    print("December")
else:
    print("Invalid month number. Please enter 1-12.")

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4. Day Number to Name Converter 🗓️

Converts day number to day name (Monday=1 to Sunday=7):

Python

day_num = int(input("Enter day number (1-7): "))
if day_num == 1:
    print("Monday")
elif day_num == 2:
    print("Tuesday")
elif day_num == 3:
    print("Wednesday")
elif day_num == 4:
    print("Thursday")
elif day_num == 5:
    print("Friday")
elif day_num == 6:
    print("Saturday")
elif day_num == 7:
    print("Sunday")
else:
    print("Invalid day number. Please enter 1-7.")

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5. Temperature Category Classifier 🌡️

Classifies temperature into categories:

Python

temp = float(input("Enter temperature in °C: "))
if temp > 40:
    print("Extreme Heat")
elif temp > 30:
    print("Hot")
elif temp > 20:
    print("Warm")
elif temp > 10:
    print("Cool")
elif temp > 0:
    print("Cold")
else:
    print("Freezing")