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| While Loop Statements |
While Loop Statements
Python utilizes the while loop similarly to other popular languages. The while loop evaluates a condition then executes a block of code if the condition is true. The block of code executes repeatedly until the condition becomes false.
The basic syntax is:
counter = 0
while counter < 10:
# Execute the block of code here as
# long as counter is less than 10
counter += 1
An example is shown below:
days = 0
week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
while days < 7:
print("Today is " + week[days])
days += 1
Output:
Today is Monday
Today is Tuesday
Today is Wednesday
Today is Thursday
Today is Friday
Today is Saturday
Today is Sunday
Line-by-Line Explanation of the above code:
- the variable 'days' is set to a value 0.
- a variable week is assigned to a list containing all the days of the week.
- while loop begins if the variable 'days' is less than 7
- executes the code within the while loop
- the variable 'days' is increased by 1 The code will then return to line 3 and repeat until days = > 7
Infinite Loops:
As previously noted, a 'while' loop will run until the conditional logic is false. Because of this, it is important to set a "false" condition within the executable code. If no false is included, the while loop will run infinitely. Use caution when setting logic parameters to prevent the infinite loop unless that is the desired output.
Because while loops are conditioned controlled loops, they are great for programs that need to be run for an indefinite number of times. This allows for input to be taken time and time again until the condition is met. A good practical example would be for a game in which the player has the option to try again. Until the player responds with the response that meets the while loop condition, the player can continue to play the game, simulating the loop as many times as they please.