How can I make sense of the else clause of Python loops?
Loops are an essential component of any programming language that helps a developer iterate over a given block of code. Python provides two types of loops – for
and while
. There is an also an optional clause associated with both loops called the else
clause. However, the else
clause of the loop is not well understood by many Python beginners.
In this article, we will take a closer look at the else
clause of Python loops and understand its purpose and usage with examples.
How does an else clause work in Python loops?
The else
clause of Python loops is a conditional statement that executes once the loop has completed its iteration except when a break
keyword is encountered. If the loop is not terminated prematurely using the break
statement, then the else
block is executed.
The else
block can be used either with a for loop
or a while loop
. Here is the syntax of the else
clause in Python loops.
for variable in sequence:
# Code block to iterate.
else:
# Code block to execute once the loop has completed iteration
while condition:
# Code block to iterate.
else:
# Code block to execute once the loop has completed iteration.
Let’s see some examples to make it easier to understand.
Example 1: Using the else clause with a for loop
Suppose we want to find the multiplication of numbers in the following list.
numbers = [1, 2, 3, 4, 5]
We can use a for loop
to iterate over the numbers list and calculate the product of all numbers. Here’s how we can do it:
numbers = [1, 2, 3, 4, 5]
result = 1
for number in numbers:
result *= number
else:
print("The multiplication of all numbers is: ", result)
In this example, once the for loop
has finished iterating over the numbers
list, the else
block is executed, and the final result is printed.
Example 2: Using the else clause with a while loop
Let’s now take an example of the else
clause with a while loop
. Suppose a user enters a number from the keyboard. The program iterates through it and checks whether the entered number is even or odd. If it is even, then the loop executes the code block to print a message. If the user enters an odd number, the loop will break.
number = int(input("Enter a number: "))
while number % 2 == 0:
print("Please enter an odd number")
number = int(input("Enter a number: "))
else:
print("Perfect! You entered an odd number")
In this example, if the user enters an even number, then the loop will continue to run, and the code block will execute. Once the user has entered an odd number, the while loop
is terminated, and the else
clause is executed.
Conclusion
In conclusion, the else
clause in Python loops is a powerful and optional component used when we want to execute specific code after completing the iteration of the loop. We can use the else
clause either with a for loop
or while loop
. We have demonstrated some examples of how to use the else
clause with both loops to make it easier to understand. We hope it has helped clarify the use of the else
clause in Python loops.