Python while Loop | mstvlife
Circles are one of the principal ideas of programming dialects. Circles are helpful when you need to rehash a particular square of code various occasions until a given condition is met.
There are two basic loop constructs in Python,
This tutorial covers the basics of
while loops in Python. We’ll also show you how to use the
else clause and the
while Loop #
while loop executes its statements an unknown number of times as long as the given condition evaluates to
while loop takes the following form:
while EXPRESSION: STATEMENT(S)
while statement starts with the
while keyword, followed by the conditional expression.
The EXPRESSION is assessed before executing the announcements. In the event that the condition assesses to genuine, the STATEMENT(S) are executed. Something else, if the condition assesses to bogus, the circle is ended, and the program control is passed to the explanation that follows.
The STATEMENT(S) square beginnings with a space and finishes with the first unindented line. The vast majority decide to utilize either 4-space or 2 space. The official Style Guide for Python Code prescribes to utilize 4-spaces per space level and to abstain from blending the utilization of tabs and spaces for space.
Let’s look at the following example code that increments and prints the current value of the variable
i as long as it is less than five:
i=0 while i < 5: i += 1 print('number:', i)
Tue loop iterates as long as
i is less or equal than five. It will produce the following output:
number: 1 number: 2 number: 3 number: 4 number: 5
Python supports standard comparison operations:
a == b– True if
a != b– True if
bare not equal.
a > b– True if
ais greater than
a >= b– True if
ais equal or greater than
a < b– True if
ais less than
a <= b– True if
ais equal or less than
To negate the conditional expression, use the logical
i=0 while not i >= 5: i += 1 print('number:', i)
continue Statements #
continue statements allow you to control the
while loop execution.
The break articulation ends the present circle and passes program control to the explanation that follows the ended circle. The most well-known circumstance is to utilize break to end the circle when a specific condition is met.
In the following example, the execution of the loop is interrupted once the current iterated item is equal to
i=0 while i < 5: i += 1 if i == 2: break print('number:', i)
continue statement exits the current iteration of a loop and passes program control to the next iteration of the loop.
In the following below, once the current iterated item is equal to
continue statement will cause execution to return to the beginning of the loop and to continue with the next iteration.
i=0 while i < 5: i += 1 if i == 2: continue print('number:', i)
number: 1 number: 3 number: 4 number: 5
else Clause #
Unlike other languages, in Python, the
while loop has an optional
while EXPRESSION: STATEMENT(S) else: STATEMENT(S)
The statements inside the
else clause are executed only when the
EXPRESSION evaluates to
false. If an exception is raised or if the loop is terminated with the
break statement, it won’t be executed.
Here is an example:
i=0 while i < 5: i += 1 print('number:', i) else: print('Loop completed.')
number: 1 number: 2 number: 3 number: 4 number: 5 Loop completed.
Now lew’s see what happens when you
break out of the loop:
i=0 while i < 5: i += 1 if i == 2: break print('number:', i) else: print('Loop completed.')
The statement inside the
else clause is not executed because the expression did not evaluate to
else clause with a
while loop is not often used. One common situation is when you expect to break from a loop, and if the loop continues to run until the condition evaluate to
false, you can execute some statement or function.
while Loop #
A vast circle is a circle that rehashes inconclusively and never ends until the program ends. In the event that the condition consistently assesses to genuine, you get a boundless circle.
Infinite loops are generally used to make the program wait for some external event to occur. Typically, in Python, an infinite loop is created with
while True: Instead of
True, you can also use any other expression that always returns
Here is an example of an infinite
while loop that will continue to prompt you to enter “Yes”:
while True: i = input('Please enter 'Yes': ') if i.strip() == 'Yes': break
while loop above will run until you enter “Yes”:
Please enter 'Yes': 3 Please enter 'Yes': l Please enter 'Yes': lin Please enter 'Yes': No Please enter 'Yes': Yes
Another way to terminate an infinite loop is to press
When writing infinite loops, make sure you use the
break statement to exit the loop at some point.
The while circle over and over executes its announcements as long the given condition assesses to genuine.
If you have any questions or feedback, feel free to leave a comment.