while循环语句及练习题
Python 编程中 while 语句用于循环执行程序，即在某条件下，循环执行某段程序，以处理需要重复处理的相同任务。其基本形式为： while 判断条件： 执行语句...... 执行语句可以是单个语句或语句块。判断条件可以是任何表达式，任何非零、或非空（null）的值均为true。
当判断条件假 false 时，循环结束。
实例：
count = 0
while (count < 9): print ('The count is:', count) count = count + 1 print("Good bye!") 运行结果：
The count is: 0
The count is: 1
The count is: 2 The count is: 3 The count is: 4 The count is: 5 The count is: 6 The count is: 7 The count is: 8 Good bye! continue 和 break 用法
while 语句时还有另外两个重要的命令 continue，break 来跳过循环，continue 用于跳过该次循环，break 则是用于退出循环，此外"判断条件"还可以是个常值，表示循环必定成立，具体用法如下：
i = 1
while i < 10:
i += 1
if i%2 > 0: # 非双数时跳过输出 continue print(i) # 输出双数2、4、6、8、10 运行结果：
2
4
6
8
10
i = 1
while 1: # 循环条件为1必定成立 print(i) # 输出1~10 i += 1 if i > 10: # 当i大于10时跳出循环 break 运行结果：
1
2
3
4
5 6 7 8 9 10 无限循环
如果条件判断语句永远为 true，循环将会无限的执行下去，如下实例：
var = 1
while var == 1 : # 该条件永远为true，循环将无限执行下去 num = input("Enter a number :") print ("You entered: ", num) print ("Good bye!") Enter a number :3
You entered: 3
Enter a number :4 You entered: 4 Enter a number :5 You entered: 5 Enter a number :6 You entered: 6 Enter a number :7 You entered: 7 Enter a number :8 You entered: 8 Enter a number :100 You entered: 100 Enter a number :Traceback (most recent call last): File "c:/1.py", line 76, in <module> # num = input("Enter a number :") KeyboardInterrupt 注意：以上的无限循环你可以使用 CTRL+C 来中断循环。
循环使用 else 语句
在 python 中，while … else 在循环条件为 false 时执行 else 语句块：
count = 0
while count < 5: print (count, " is less than 5") count = count + 1 else: print (count, " is not less than 5") 运行结果：
0 is less than 5
1 is less than 5
2 is less than 5 3 is less than 5 4 is less than 5 5 is not less than 5 相关练习题
1.输出1,2,3,4,5,6,8,9,10
count = 1
while count <= 10: if count == 7: pass else: print(count) count = count + 1 2.输出1-100所有数的和
n = 1
m = 0
while n < 101:
m = m + n
n = n + 1 print(m) 3.输出100以内所有奇数
n = 1
while n < 101:
temp = n % 2
if temp == 0: print(n) else: pass n = n +1 4.输出1-2+3-4+5.....99所有数的和
n = 1
m = 0
while n < 100:
temp = n % 2 if temp == 0: m = m - n else: m = m + n n = n + 1 print(m) 参考资料：
1.Python While 循环语句 | 菜鸟教程：https://www.runoob.com/python/python-while-loop.html