Control Flow: Conditional Statements and Loops

Posted on by Khalil Hijazi

Control flow statements in Python allow us to control the execution flow of our programs based on conditions and repetition. In this blog post, we will explore conditional statements (if, elif, else) and different types of loops (for, while) in Python.

Conditional Statements: if, elif, else

Conditional statements are used to execute specific blocks of code based on certain conditions. The if statement is the most basic type of conditional statement. Here’s an example:

age = 18

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

In this example, the code inside the if block will only execute if the condition age >= 18 evaluates to True. If the condition is False, the code block will be skipped.

We can also include additional conditions using the elif (short for “else if”) statement. Here’s an example:

age = 25

if age < 18:
    print("You are not eligible to vote.")
elif age >= 18 and age < 21:
    print("You can vote, but cannot drink.")
else:
    print("You can vote and drink!"

In this example, the program checks multiple conditions using if, elif, and else. The appropriate code block will be executed based on the first condition that evaluates to True.

Loops: for and while

Loops are used to repeatedly execute a block of code. Python provides two types of loops: the for loop and the while loop.

The for loop is used to iterate over a sequence of elements. Here’s an example:

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(fruit)

In this example, the for loop iterates over each element in the fruits list and prints it.

The while loop is used to repeatedly execute a block of code as long as a certain condition is True. Here’s an example:

count = 0

while count < 5:
    print("Count:", count)
    count += 1

In this example, the code inside the while loop will execute as long as the condition count < 5 is True. The count variable is incremented by 1 in each iteration.

Control Flow Keywords: break, continue, and pass

Python provides additional keywords to control the flow within loops:

  • break: Terminates the loop prematurely and moves to the next statement after the loop.
  • continue: Skips the rest of the current iteration and moves to the next iteration.
  • pass: Acts as a placeholder and does nothing. It is commonly used when a statement is required syntactically but doesn’t require any code execution.

Here’s an example that demonstrates the use of these keywords:

for num in range(1, 6):
    if num == 3:
        break  # Terminate the loop when num is 3
    elif num == 2:
        continue  # Skip the rest of the code and move to the next iteration when num is 2
    else:
        pass  # Placeholder statement, does nothing
    
    print("Number:", num)

print("Loop terminated.")

Conclusion

In this blog post, we explored conditional statements (if, elif, else) and different types of loops (for, while) in Python. Conditional statements allow us to execute specific code blocks based on conditions, while loops enable repetitive execution as long as a certain condition is true, and for loops iterate over a sequence of elements. We also learned about control flow keywords such as break, continue, and pass, which provide additional control within loops.

Understanding control flow statements and loops is crucial for building dynamic and interactive programs. They allow us to make decisions, repeat tasks, and create more efficient and flexible code.

In the next blog post, we will explore functions in Python, a powerful tool for organizing and reusing code. Stay tuned for more exciting Python programming content!

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