Python While Loops

Python while loops will be discussed in this post using examples in order to achieve the learning objectives.

Python Loops

When it comes to Python loops, there are two primitive commands:

A loop, for instance, is useful if we would like to render the same message 10 times or more numbers of times.

The while Loop

We can use Python while loops to process a set of statements as long as a condition is met.


while expression:
  • A while loop evaluates a condition.
  • While loops are executed if the condition evaluates to True.
  • The condition is re-evaluated.
  • As long as the condition remains False, the process repeats itself.
  • Whenever the condition evaluates to False, the loop ends.

Now print mrx as soon as mrx is less than 12:


mrx = 3 while mrx < 12: print(mrx) mrx += 1

Reminder:  If mrx is not incremented, the loop will continue indefinitely.

In the above example we define an indexing variable, mrx, which has the value 3. To use a while loop, relevant variables must be available.

Iterate the numbers in reverse order with a while loop:


mrx = 12 while mrx > 3: print(mrx) mrx -= 1

Python continue Statement

Using the continue statement, we can terminate the current iteration and continue with the next.

Continue to the following iteration if mrx is 7:


mrx = 1 while mrx < 12: mrx += 1 if mrx == 7: continue print(mrx)

Continue to the following iteration if mrx is 4,5,6 and 7:


mrx = 12 while mrx > 1: mrx -= 1 if mrx >= 4 and mrx <= 7: continue print(mrx)

Python break Statement

If the while condition is true, we can stop the loop with the break statement.

Stop the loop when mrx is 7:


mrx = 1 while mrx < 12: print(mrx) if mrx == 7: break mrx += 1

Now stop the while loop in reverse when mrx value is 4:


mrx = 12 while mrx > 3: print(mrx) if mrx == 4: break mrx -= 1

Python else Statement

In Python while loops, else statement allows us to run a block of code once when the condition does not apply.

Display a message once the condition is invalid:


mrx = 1 while mrx < 12: print(mrx) mrx += 1 else: print("mrx is no more smaller than twelve")

Display a message once the condition is invalid In reverse While loop:


mrx = 12 while mrx > 1: print(mrx) mrx -= 2 else: print("mrx is no longer smaller than Two")

Python while loops examples

Python While loops vs for loops:

There is one main difference between the for loop and Python while loops; the for loop is commonly applied when the number of iterations is predetermined and the while loop is usually called for when the number of iterations is undetermined.

Python While Loop uses

Python While loop is used for various purposes such as:

  1. The while loop in Python allows you to iterate over a sequence of elements until a specific condition is met. For example, you can use a while loop to iterate over a list, string, or any other iterable object, performing certain operations on each element until a condition becomes false.
  2. While loops are commonly used when you need to repeat a block of code until a particular condition evaluates to false. You can specify the condition at the beginning of the loop, and as long as the condition remains true, the loop will continue executing. This is useful for implementing tasks such as user input validation, menu-driven programs, or waiting for specific events to occur.
  3. While loops can be used to create infinite loops where the condition is always true. This can be useful when you want a section of code to run continuously until you explicitly break out of the loop. Infinite loops are commonly used in scenarios such as server applications or event-driven programming, where the program needs to run indefinitely until a termination condition is met.
  4. The condition of a while loop can be updated within the loop body, allowing you to dynamically control the flow of execution. This means that you can change the condition based on certain actions or events occurring during each iteration. This flexibility gives you greater control over the behavior of your program and allows for more complex and adaptive logic.
  5. While loops are an essential component for implementing various algorithms and solving problems. They can be used to implement iterative algorithms like binary search or numerical methods, where the solution is refined through multiple iterations until a desired accuracy or condition is achieved. While loops provide a way to iteratively update variables and make progress towards a solution until the termination condition is met.
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