Python中用while语句和for语句表示循环执行某一段代码

while后面跟一个条件，或者跟一个序列（列表、元组等），序列为空则跳出循环，否则继续循环

for循环后面跟一个序列，循环次数为序列的长度

while循环可以加个else语句，跳出while的时候就执行这个else

举例

a = 3 while a > 0: print(a) a -= 1

输出： 3 2 1

shoplist = ['apple', 'mango', 'carrot', 'banana'] while shoplist: print(3)

输出：一直输出3，直到按ctrl+c

shoplist = ['apple', 'mango', 'carrot', 'banana'] while shoplist: print(3) shoplist = shoplist[:(len(shoplist)-1)]#每次循环都去掉最后一个元素

输出： 3 3 3 3

shoplist = ['apple', 'mango', 'carrot', 'banana'] while shoplist: print(3) shoplist = shoplist[:(len(shoplist)-1)] else: print('finished')#else语句

输出： 3 3 3 3 finished

shoplist = ['apple', 'mango', 'carrot', 'banana'] for i in shoplist: print(i) #这里面i会被逐次赋值为shoplist里面的元素

输出： apple mango carrot banana

shoplist = ('apple', 'mango', 'carrot', 'banana') for i in shoplist: print(i) #这里shoplist是元组，for循环也可以跟元组

输出： apple mango carrot banana