'''while 语句：格式：while 表达式：    语句逻辑：当程序遇到while语句的时候，首先计算【表达式】的值      如果【表达式】的值为假，那么结束整个while语句      如果表达式的值为真，则执行【语句】，循环调用，直到为假停止'''#从1打印到小于5的数num = 1while num < 5:    print("num = %d"% num)    num += 1#计算1+2+3+...+100sum = 0num = 1while num <= 100:    sum += num    num += 1    #print("sum = %d" % sum)print("sum = %d"% sum)#打印字符串里的每一个字符str = "My name is jjking."index = 0while index <= len(str):    print(str[index])    index += 1

运行结果：

num = 1num = 2num = 3num = 4sum = 5050My name is jjking.