给定以下代码(不起作用):

while True:
    # Snip: print out current state
    while True:
        ok = get_input("Is this ok? (y/n)")
        if ok.lower() == "y": break 2 # This doesn't work :(
        if ok.lower() == "n": break

    # Do more processing with menus and stuff

有办法解决这个问题吗?还是我必须先检查一次,跳出输入循环,然后再检查一次,如果用户满意,再跳出外部循环?


当前回答

这不是最漂亮的方法,但在我看来,这是最好的方法。

def loop():
    while True:
    #snip: print out current state
        while True:
            ok = get_input("Is this ok? (y/n)")
            if ok == "y" or ok == "Y": return
            if ok == "n" or ok == "N": break
        #do more processing with menus and stuff

我很确定你也可以用递归解出一些东西,但我不知道这对你来说是不是一个好选择。

其他回答

可能像下面这样的小技巧会做,如果不喜欢重构成函数

增加了1个break_level变量来控制while循环条件

break_level = 0
# while break_level < 3: # if we have another level of nested loop here
while break_level < 2:
    #snip: print out current state
    while break_level < 1:
        ok = get_input("Is this ok? (y/n)")
        if ok == "y" or ok == "Y": break_level = 2 # break 2 level
        if ok == "n" or ok == "N": break_level = 1 # break 1 level
# this version uses a level counter to choose how far to break out

break_levels = 0
while True:
    # snip: print out current state
    while True:
        ok = get_input("Is this ok? (y/n)")
        if ok == "y" or ok == "Y":
            break_levels = 1        # how far nested, excluding this break
            break
        if ok == "n" or ok == "N":
            break                   # normal break
    if break_levels:
        break_levels -= 1
        break                       # pop another level
if break_levels:
    break_levels -= 1
    break

# ...and so on

下面是一个似乎可以工作的实现:

break_ = False
for i in range(10):
    if break_:
        break
    for j in range(10):
        if j == 3:
            break_ = True
            break
        else:
            print(i, j)

唯一的缺点是你必须在循环之前定义break_。

Break for外层和内部while循环:

while True:
    while True:
        print('Breaks inner "while" loop')
        break # Here
    print('Breaks outer "while" loop')
    break # Here

或者,用if语句中断外部和内部while循环:

while True:
    while True:
        if True:
            print('Breaks inner "while" loop')
            break # Here
    print('Breaks outer "while" loop')
    break # Here

输出:

Breaks inner "while" loop
Breaks outer "while" loop

Break for outer和inner for循环:

for _ in iter(int, 1):
    for _ in iter(int, 1):
        print('Breaks inner "for" loop')
        break # Here
    print('Breaks outer "for" loop')
    break # Here

或者,用if语句打破外部和内部for循环:

for _ in iter(int, 1):
    for _ in iter(int, 1):
        if True:
            print('Breaks inner "for" loop')
            break # Here
    print('Breaks outer "for" loop')
    break # Here

输出:

Breaks inner "for" loop
Breaks outer "for" loop

和上一台很像,但更紧凑。 (布尔值只是数字)

breaker = False #our mighty loop exiter!
while True:
    while True:
        ok = get_input("Is this ok? (y/n)")
        breaker+= (ok.lower() == "y")
        break

    if breaker: # the interesting part!
        break   # <--- !