While 循环

Python for Developers 入门

Jasmin Ludolf

Senior Data Science Content Developer

If 语句

if 语句流程：开始 > 条件满足 > 执行动作 > 退出

If 语句 vs while 循环

If 语句

if 语句流程：开始 > 条件满足 > 执行动作 > 退出

While 循环

while 循环流程：开始 > 条件满足 > 执行动作 > 循环 > 直到条件不再满足为止

While 循环

while condition:
    action

任何持续性的任务
- 按住按钮时加速

带赛车游戏的游戏机

¹ https://unsplash.com/@joaoscferrao

While 循环

ingredients_to_add = 5
items_added = 0

# 还有剩余就继续添加
while items_added < ingredients_to_add:

    items_added += 1
    remaining = ingredients_to_add - items_added
    print(remaining, "ingredients left to add")

输出

4 ingredients left to add
3 ingredients left to add
2 ingredients left to add
1 ingredients left to add
0 ingredients left to add

当 items_added 等于 ingredients_to_add 时循环退出

注意事项

while 在条件满足时持续运行

ingredients_to_add = 5
items_added = 0

while items_added < ingredients_to_add:
    remaining = ingredients_to_add - items_added
    print(remaining, "ingredients left")

永远运行

ingredients_to_add = 5
items_added = 0

# 无限循环 - 永不退出！
while items_added < ingredients_to_add:
    remaining = ingredients_to_add - items_added
    print(remaining, "ingredients left")
    # 忘记递增 items_added！

条件永远不会变为 False
循环一直运行，程序卡死
开发者常见错误

中断循环

while items_added < ingredients_to_add:
    remaining = ingredients_to_add - items_added
    print(remaining, "ingredients left")


    # 终止循环
    break

break 也可用于 for 循环
若代码已在运行：Control + C / Command + C

while 中的条件语句

ingredients_to_add = 5
items_added = 0


while items_added < ingredients_to_add:
    items_added += 1
    remaining = ingredients_to_add - items_added

    if remaining > 3:
        print("Several ingredients remaining")

    elif remaining >= 1:
        print("Almost done!")

    else:
        print("Shopping list complete!")

条件语句的输出

Several ingredients remaining
Several ingredients remaining
Almost done!
Almost done!
Shopping list complete!

Passons à la pratique !

Python for Developers 入门