Python – Control Flow

Introduction to Control Flow in Python

Control flow is an essential concept in programming that allows the execution of code to be controlled based on certain conditions. In Python, control flow is achieved through the use of conditional statements and loops. These tools enable developers to create programs that can make decisions and repeat tasks based on specific conditions.

Conditional Statements: if, elif, and else

The if statement is the most fundamental conditional statement in Python. It allows you to execute a block of code only if a certain condition is true. Here’s an example:

age = 18
if age >= 18:
    print("You are an adult")

In this example, the code inside the if block will only be executed if the variable age is greater than or equal to 18. If the condition is not met, the code inside the if block will be skipped.

Python also provides the elif and else statements to handle multiple conditions. The elif statement allows you to check for additional conditions if the previous conditions are not met. The else statement is used to execute code when none of the previous conditions are true. Here’s an example:

age = 15
if age >= 18:
    print("You are an adult")
elif age >= 13:
    print("You are a teenager")
else:
    print("You are a child")

In this example, if the age is 15, the code inside the elif block will be executed since the first condition is not met. If the age is less than 13, the code inside the else block will be executed.

Loops: for and while

Loops allow you to repeat a block of code multiple times. Python provides two types of loops: for and while.

The for loop is used to iterate over a sequence (such as a list, tuple, or string) or other iterable objects. Here’s an example:

fruits = ["apple", "banana", "orange"]
for fruit in fruits:
    print(fruit)

In this example, the for loop iterates over each element in the fruits list and prints it. The loop will continue until all the elements have been processed.

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 += 1

In this example, the while loop will continue to execute as long as the count variable is less than 5. The count variable is incremented by 1 in each iteration to eventually exit the loop.

Control Flow with Break and Continue

In addition to conditional statements and loops, Python also provides the break and continue statements to control the flow of execution within loops.

The break statement is used to terminate the loop prematurely. When encountered, it immediately exits the loop and resumes execution at the next statement after the loop. Here’s an example:

fruits = ["apple", "banana", "orange"]
for fruit in fruits:
    if fruit == "banana":
        break
    print(fruit)

In this example, the loop will stop when it encounters the element “banana”. The code after the break statement will not be executed.

The continue statement is used to skip the rest of the current iteration and move on to the next iteration of the loop. Here’s an example:

fruits = ["apple", "banana", "orange"]
for fruit in fruits:
    if fruit == "banana":
        continue
    print(fruit)

In this example, when the loop encounters the element “banana”, it will skip the print(fruit) statement and move on to the next iteration.

Conclusion

Control flow is a fundamental concept in programming, and Python provides powerful tools to control the execution of code based on conditions and to repeat tasks using loops. By understanding and utilizing control flow statements such as if, elif, else, for, while, break, and continue, you can create more dynamic and flexible programs in Python.