Python Conditional Statements and Loops

Conditional statements and loops are essential pillars of Python programming, forming the foundation for creating dynamic, efficient, and intelligent code. These powerful constructs allow developers to automate decision-making processes and execute repetitive tasks with ease, making them indispensable tools for beginners and seasoned programmers alike. Whether you’re designing a simple script or building a complex application, mastering conditional statements and loops will empower you to control the flow of your program and handle a wide variety of scenarios effectively. In this tutorial, we’ll dive deep into the world of Python’s conditional statements—such as if, elif, and else—which enable your program to make decisions based on specific conditions, much like how we choose different paths in everyday life depending on the situation. We’ll also explore loops, including for and while, which allow you to repeat blocks of code efficiently, eliminating the need for tedious manual repetition. By understanding how to harness these tools, you’ll unlock the ability to write cleaner, more logical, and highly functional programs.

1. Conditional Statements

Conditional statements in Python execute a piece of code only if certain conditions are met. These statements help your code to make decisions automatically.

if statements

The simplest conditional statement is the if statement:

age = 20
if age >= 18:
    print("You are eligible to vote!")

Output:

You are eligible to vote!

if-else statements

Use if-else when you want to execute one block if the condition is true and another if it’s false:

temperature = 35
if temperature > 30:
    print("It's hot!")
else:
    print("It's not hot.")

Output:

It's hot!

if-else if-else statements

Use elif (short for “else if”) to check multiple conditions:

grade = 85

if grade >= 90:
    print("Excellent!")
elif grade >= 75:
    print("Good job!")
elif grade >= 50:
    print("Passed!")
else:
    print("Failed!")

Output:

Good job!

2. Loops

Loops are used to repeat a sequence of actions until a certain condition is met. Python has two types of loops: for loops and while loops.

for loops

A for loop is used to iterate over elements of a sequence (e.g., a list, tuple, or string).

# Iterate over a list
fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
    print(fruit)

Output:

apple
banana
cherry

You can also use the range() function to repeat actions a set number of times:

# Print numbers from 1 to 5
for i in range(1, 6):
    print(i)

Output:

1
2
3
4
5

while loops

The while loop repeats a block of code as long as a condition remains true:

count = 0
while count < 3:
    print("Count:", count)
    count += 1

Output:

Count: 0
Count: 1
Count: 2

Note: Be careful of infinite loops (when the condition never becomes false):

# Example of an infinite loop
# while True:
#     print("This loop never ends!")

3. Loop Control Statements

Python provides special statements to control loops:

break

The break statement exits the loop immediately.

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

Output:

0
1
2
3
4

continue

The continue statement skips the current iteration and continues with the next:

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

Output:

0
1
3
4

pass

pass does nothing. It’s often used as a placeholder:

for number in range(3):
    if number == 1:
        pass  # Future code goes here
    print(number)

Output:

0
1
2

4. Nested Loops and Conditionals

You can combine loops and conditional statements:

# Print multiplication table for 1 to 3
for i in range(1, 4):
    for j in range(1, 4):
        print(f"{i} x {j} = {i * j}")

Output:

1 x 1 = 1
1 x 2 = 2
1 x 3 = 3
2 x 1 = 2
2 x 2 = 4
2 x 3 = 6
3 x 1 = 3
3 x 2 = 6
3 x 3 = 9