When is while loop used

List Methods. Dictionary Methods. String Methods. Start Learning Python. Explore Python Examples. Related Topics Python Looping Techniques. Python break and continue. Python Statement, Indentation and Comments. Python while Loop Loops are used in programming to repeat a specific block of code. Video: Python while Loop. What is while loop in Python? We generally use this loop when we don't know the number of times to iterate beforehand. In Python, the body of the while loop is determined through indentation.

The body starts with indentation and the first unindented line marks the end. The while loop can be thought of as a repeating if statement. There are two commonly used test before loops in the iteration or repetition category of control structures. They are: while and for. This module covers the: while. The concept of iteration is connected to possibly wanting to repeat an action. Like all control structures we ask a question to control the execution of the loop.

The term loop comes from the circular looping motion that occurs when using flowcharting. The basic form of the while loop is as follows:. In most programming languages the question called a test expression is a Boolean expression. The Boolean data type has two values — true and false. Within the while control structure there are four attributes to a properly working loop.

They are:. The initialization of the flag is not technically part of the control structure, but a necessary item to occur before the loop is started. This is looping on the true. When the test expression is false, you stop the loop and go on with the next item in the program. Notice, because this is a test before loop the action might not happen. If the action inside the loop does not modify the variables being tested in the loops condition, the loop will "run" forever.

For example:. A design pattern is the syntax that you have to memorize in order to do well in programming and on tests. The "While" Loop A "While" Loop is used to repeat a specific block of code an unknown number of times, until a condition is met. The basic form of the do while loop is as follows:.

In most programming languages the question called a test expression is a Boolean expression. The Boolean data type has two values — true and false. Within the do while control structure there are three attributes of a properly working loop.

They are:. This is looping on the true. When the test expression is false, you stop the loop and go on with the next item in the program. Notice, because this is a test after loop the action will always happen at least once. It is called a test after loop because the test comes after the action. It is also sometimes called a post-test loop, meaning the test is post or Latin for after the action and update.

The basic form of the repeat until loop is as follows:. Within the repeat until control structure, there are three attributes of a properly working loop.