Conditional statements allow us to execute different blocks of code based on certain conditions. In Python, the primary conditional statements are:

1. if statement
2. elif statement
3. else statement

These statements work together to check for conditions and execute code accordingly.

The if statement is used to test a condition. If the condition is True, the block of code under the if statement is executed. Otherwise, the block of code is skipped.

if condition:
    # Code to execute if condition is True

age = 18

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

The else statement is used to execute a block of code if the if condition is False.

if condition:
    # Code to execute if condition is True
else:
    # Code to execute if condition is False

age = 16

if age >= 18:
    print("You are eligible to vote.")
else:
    print("You are not eligible to vote.")

The elif (short for "else if") statement allows you to check multiple conditions. If the first if condition is False, it checks the elif condition. If the elif condition is True, the code block under elif is executed. You can have multiple elif statements.

if condition1:
    # Code to execute if condition1 is True
elif condition2:
    # Code to execute if condition2 is True
else:
    # Code to execute if all conditions are False

marks = 75

if marks >= 90:
    print("Grade: A")
elif marks >= 80:
    print("Grade: B")
elif marks >= 70:
    print("Grade: C")
else:
    print("Grade: D")

You can have if statements inside other if statements. This is called nesting. Nested if statements are useful when you need to check multiple conditions at different levels

if condition1:
    # Code to execute if condition1 is True
    if condition2:
        # Code to execute if condition2 is True
    else:
        # Code to execute if condition2 is False
else:
    # Code to execute if condition1 is False

number = 15

if number > 10:
    print("Number is greater than 10.")
    if number % 2 == 0:
        print("Number is even.")
    else:
        print("Number is odd.")
else:
    print("Number is 10 or less.")

You can combine multiple conditions using logical operators like and, or, and not to form complex conditions.

- and Operator: Returns True if both conditions are True.
- or Operator: Returns True if at least one of the conditions is True.
- not Operator: Reverses the result of the condition.

age = 20
has_voter_id = True

if age >= 18 and has_voter_id:
    print("You are eligible to vote.")
else:
    print("You are not eligible to vote.")

Python supports a shorter syntax for writing if...else statements using conditional expressions, also known as the ternary operator.

value_if_true if condition else value_if_false

age = 18
status = "Eligible" if age >= 18 else "Not eligible"
print(status)  # Output: Eligible

Write a Python program that takes the age of a person as input and checks whether the person is eligible to vote or not. (Age should be 18 or above to be eligible.)

Write a Python program that takes the marks of a student as input and prints the grade based on the following criteria:
Marks >= 90: Grade A
Marks >= 80: Grade B
Marks >= 70: Grade C
Marks >= 60: Grade D
Marks < 60: Grade F

Write a Python program to check if a given year is a leap year or not. A leap year is exactly divisible by 4, except for years that are exactly divisible by 100. However, years divisible by 400 are leap years.

Write a Python program that takes a number as input and checks whether the number is odd or even.

Create a simple calculator that takes two numbers and an operator (+, -, *, /) as input and performs the corresponding operation using if-elif-else statements.

Write a Python program that takes the weight (in kg) and height (in meters) of a person as input and calculates their Body Mass Index (BMI). The program should then categorize the BMI as:
BMI < 18.5: Underweight
18.5 <= BMI < 24.9: Normal weight
25 <= BMI < 29.9: Overweight
BMI >= 30: Obesity

Write a Python program that takes an integer as input and checks if it is positive, negative, or zero

Create a Python program that takes a password as input and checks its strength based on the following criteria:
At least 8 characters long
Contains both uppercase and lowercase characters
Contains at least one digit
Contains at least one special character (e.g., @, #, !)

Write a Python program that takes a person's age and income as input and prints whether the person has to pay taxes. The tax rules are:
If the age is less than 18, they do not need to pay taxes.
If the age is between 18 and 60, they need to pay taxes if their income is more than 5 lakh.
If the age is above 60, they need to pay taxes if their income is more than 3 lakh.

Loops allow you to execute a block of code multiple times. Python provides two types of loops:

Both loops are used to perform repetitive tasks but have different use cases and syntax.

The while loop executes a block of code as long as the given condition is True. It is primarily used when the number of iterations is not known beforehand.

while condition:
    # Code to execute repeatedly as long as the condition is True

count = 0
while count < 5:
    print("Count is:", count)
    count += 1  # Increment count by 1

A while loop can become an infinite loop if the condition never becomes False. You need to be careful to include a condition that will eventually break the loop.

while True:
    print("This will run forever if not stopped!")

The for loop is used to iterate over a sequence (like a list, tuple, string, or range). It is most commonly used when the number of iterations is known beforehand.

for variable in sequence:
    # Code to execute for each element in the sequence

for i in range(5):
    print("Value of i:", i)

print(list(range(5)))        # Output: [0, 1, 2, 3, 4]
print(list(range(2, 7)))     # Output: [2, 3, 4, 5, 6]
print(list(range(1, 10, 2))) # Output: [1, 3, 5, 7, 9]

A loop inside another loop is called a nested loop. The inner loop runs completely whenever the outer loop runs once.

for i in range(1, 4):
    for j in range(1, 4):
        print(f"i={i}, j={j}")

i=1, j=1
i=1, j=2
i=1, j=3
i=2, j=1
...

for i in range(5):
    if i == 3:
        break
    print(i)
# Output: 0 1 2

for i in range(5):
    if i == 3:
        continue
    print(i)
# Output: 0 1 2 4

for i in range(5):
    if i == 3:
        pass  # Placeholder, does nothing
    print(i)
# Output: 0 1 2 3 4

for i in range(5):
    print(i)
else:
    print("Loop completed successfully.")

count = 0
while count < 5:
    print(count)
    count += 1
else:
    print("Loop completed successfully.")