循环

说明：  控制条件语句的变量，在for循环结束后，就不可以被访问了，而while循环还可以访问，如果你继续想使用该变量，则可以使用while循环，否则推荐使用for循环，原因是for循环结束，该变量就从内存中消失，能够提高内存的使用效率。(The variable that controls the conditional statement is not accessible after the for loop has finished, and the while loop is accessible if you continue to use the variable, you can use the while loop. Otherwise, it is recommended to use the for loop, because the variable disappears from memory after the for loop, which can improve memory efficiency.)