In Python, a while loop is a control flow statement that allows a program to repeat a paragraph under specific conditions.
Unlike traditional for loops, while loops are executed when the conditions are met until the conditions are no longer satisfied. Autumn and Winter Check-in Challenge
Basic structure. The basic structure of a while loop is as follows:
while condition: (tab) Executed block.
Here, "condition" is an expression that returns true or false.
As long as the condition is true, the program will always execute the "executed block". It is worth noting that the cycle stops immediately when the conditions are no longer met.
Therefore, when using a while loop, you must make sure that there is a termination condition, otherwise the loop may go on indefinitely, causing the program to crash.
Usage scenarios. Repeat input: When you need to get a series of data from the user, you can use a while loop to repeatedly prompt the user for input until the user has entered the data that meets the requirements.
For example, the following ** will ask the user to enter a number until the user has entered a valid integer:
user_input = input("Please enter a number:") while not user_input.isdigit(): If the user input is not a number, the cycle continues (tab)user input = input(.)"Please re-enter a number:") print("The number you enter is:", user_input)
Simulation loop: In situations where a series of actions need to be simulated, such as turn-based battles in the game, simulated traffic lights, etc., a while loop can be used to repeat each action until the termination condition is reached.
For example, the following ** simulates a simple traffic light system:
import time green light = true while true: infinite loop (tab)if green light: (2tab)print("Green light, vehicle traffic!") (2tab)time.sleep(1) Wait 1 second (tab)else: (2tab)print("Red light, vehicle stops!") (2tab)time.sleep(1) Wait for 1 second (tab)green light = not green light Toggle the color of the light.
Iterative processing: When you need to iterate on a large amount of data, you can use a while loop to process the data one by one.
For example, the following ** uses a while loop to calculate the sum of all the numbers in a list:
my list = [1, 2, 3, 4, 5] total = 0 index = 0 while index < len(my list): When the index is less than the length of the list, continue the loop (tab)total += my list[index] to add the current element to the sum (tab)index += 1 to add 1 to the index to process the next element print("The sum of all numbers in the list is:", total)
Precautions. Avoid infinite loops: When using while loops, you must ensure that there is a termination condition.
Otherwise, the program may get stuck in an infinite loop, causing the program to crash. Therefore, when designing a loop, it is important to carefully consider the termination conditions.
Use break to terminate early: In some cases, it may be necessary to terminate the loop early when certain conditions are met. In this case, you can use the break statement to break out of the loop.
Summary. A while loop is a powerful control flow statement that allows a program to repeat a paragraph based on specific conditions.
In addition to the use cases mentioned above, while loops can be used in many other cases, such as simulation loops, iterative processing, etc.
As long as you need to repeat a ** until the termination condition is met, you can consider using a while loop.