Day 3 of Learning Python for Data Science

Understanding Python’s conditional statements is essential for controlling the flow of a program. Today, we will explore if-else conditions, nested conditions, and special control statements like break, continue, and pass.

Conditional Statements

If Statement

Definition: The if statement is used to execute a block of code only if a specified condition is true.

Example:

x = 10
if x > 5:
    print("x is greater than 5")

Output:

x is greater than 5

If-Else Statement

Definition: The if-else statement allows us to execute one block of code when a condition is true and another when it is false.

Example:

num = 7
if num % 2 == 0:
    print("Even")
else:
    print("Odd")

Output:

Odd

Elif Statement

Definition: The elif statement allows checking multiple conditions sequentially.

Example:

score = 85
if score >= 90:
    print("Excellent")
elif score >= 75:
    print("Good")
else:
    print("Needs Improvement")

Output:

Good

Nested If Statements

Definition: A nested if statement is an if statement inside another if statement, allowing multiple layers of conditions.

Example:

x = 15
if x > 10:
    if x < 20:
        print("Between 10 and 20")

Output:

Between 10 and 20

Break Statement

Definition: The break statement exits a loop or control structure prematurely when a specified condition is met.

Example:

for i in range(10):
    if i == 5:
        break
    print(i)

Output:

0
1
2
3
4

Continue Statement

Definition: The continue statement skips the current iteration and moves to the next one.

Example:

for i in range(5):
    if i == 2:
        continue
    print(i)

Output:

0
1
3
4

Pass Statement

Definition: The pass statement is a placeholder that allows defining an empty code block without causing an error.

Example:

def my_function():
    pass  # Placeholder for future code

(No output as pass does nothing.)

Practice Questions

What will be the output of the following code?

x = 10
if x > 5:
    print("Greater")
else:
    print("Smaller")

Write a Python program using an if-else statement to check if a number is positive, negative, or zero.

What will be the output of the following code?

num = 7
if num % 2 == 0:
    print("Even")
else:
    print("Odd")

What will be the output of the following nested if condition?

x = 15
if x > 10:
    if x < 20:
        print("Between 10 and 20")

Write a Python program that uses nested if statements to check whether a given number is positive, even, and greater than 10.

What is the output of the following program?

pythonCopyEditx = 5
y = 10
if x > 2:
    if y > 5:
        print("Valid")

Write a Python program that asks for a user’s age and prints whether they are a child (0-12), teenager (13-19), adult (20-59), or senior (60+).

What will be the output of the following code?

x = 50
if x >= 50:
    if x == 50:
        print("Exactly 50")
    else:
        print("Greater than 50")
else:
    print("Less than 50")

Write a Python program using the pass statement inside an empty if condition.

What will the following program print?

x = 20
y = 30
if x < y:
    if x + 10 == y:
        print("Match")

Write a Python program that prints whether a number is positive or negative using an if-else statement.

Modify the code below to use an elif condition to check whether a number is positive, negative, or zero.

num = int(input("Enter a number: "))
if num > 0:
    print("Positive")
else:
    print("Negative or Zero")

What is the output of this code snippet?

x = 10
if x > 5:
    print("High")
if x > 8:
    print("Higher")
if x > 15:
    print("Highest")

Write a program that takes a number as input and prints whether it is divisible by both 2 and 3 using a nested if statement.

Write a Python program that checks if a number is a multiple of both 4 and 6 using a nested if statement.

Modify the program below to check whether a number is even and greater than 10.

num = int(input("Enter a number: "))
if num % 2 == 0:
    print("Even")

Write a Python program using if-elif-else conditions to categorize a number into small (1-10), medium (11-50), or large (above 50).

What is the output of this nested condition?

x = 3
y = 9
if x < 5:
    if y > 8:
        print("Success")

Modify the program below to check if a number is between 10 and 50 using a conditional statement.

num = int(input("Enter a number: "))
if num > 10:
    print("Valid")

Write a Python program that checks if a number is prime using conditional statements.

The answer for these is shared here: click here for answers

Conclusion

This lesson covers essential control flow structures in Python, such as conditional statements and control keywords. Understanding these concepts is crucial for writing efficient and logical Python programs. In the next session, we will explore loops and how they help automate repetitive tasks in Python.

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