python-循环 while

#python while 循环语句
numbers=[12,37,5,42,8,3]
even=[]
old=[]
while len(numbers)>0:
    num=numbers.pop()
    if num%2==0:
        even.append(num)
        print('even',even)
    else:
        old.append(num)
        print('old',old)

　　预期结果

old [3]
even [8]
even [8, 42]
old [3, 5]
old [3, 5, 37]
even [8, 42, 12]

　　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

#continue跳过该次循环
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

　　

for 循环

fruits = ['banana', 'apple', 'mango']
for fruit in fruits: 
    print('当前水果 :', fruit)
print ("Good bye!")

通过索引

fruits = ['banana', 'apple', 'mango']
for index in range(len(fruits)):
   print ('当前水果 :', fruits[index])
print ("Good bye!")

使用内置 enumerate 函数进行遍历

sequence = [12, 34, 34, 23, 45, 76, 89]
for i, j in enumerate(sequence):
    print(i,j)

预期：

0 12
1 34
2 34
3 23
4 45
5 76
6 89