Usage of while

The usage of while is "while condition: code block". The condition is an expression. When the condition is true, the code block is executed, and then it is judged again whether the condition is true. If it is true, the code block continues to be executed. , until the condition is false. while is a commonly used loop control statement, used to repeatedly execute a block of code when certain conditions are met.

while is a commonly used loop control statement, used to repeatedly execute a block of code when certain conditions are met. Its basic syntax structure is as follows:

while 条件:
    代码块

Among them, the condition is an expression. When the condition is true (True), the code block is executed, and then it is judged again whether the condition is true. If it is true, the code continues to be executed. block until the condition is False.

The execution process of the while loop can be represented by the following pseudo code:

判断条件是否为真
如果条件为真:
    执行代码块
    返回到判断条件是否为真的步骤
否则:
    结束循环

The following uses a simple example to illustrate the usage of while.

count = 0
while count < 5:
    print("当前计数：", count)
    count += 1

In the above code, we define a variable count and initialize it to 0. Then, through the while loop, it is judged whether the count is less than 5. If the condition is met, the statement in the code block is executed, the value of the current count is printed, and the count is increased by 1. Then judge again whether count is less than 5. If the condition is met, continue to execute the loop until count is no longer less than 5.

Run the above code, the following results will be output:

当前计数： 0
当前计数： 1
当前计数： 2
当前计数： 3
当前计数： 4

As you can see, the loop is executed 5 times, and the current count value is printed out each time. When count reaches 5, the condition is no longer met and the loop ends.

It should be noted that if the condition is false at the beginning, then the code block in the while loop will not be executed and the loop will be skipped directly.

In addition, in order to avoid falling into an infinite loop, we need to modify the control conditions inside the loop body to ensure that the condition is false at a certain moment, thus ending the loop. Otherwise, the loop will continue to execute and the program will not terminate.

To sum up, the usage of while loop is to control the execution of the loop by judging whether the condition is true. When the condition is true, execute the code block in the loop body; when the condition is false, jump out of the loop. By properly setting the conditions and code within the loop body, we can achieve flexible loop control to solve various problems.

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