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

尝试使用无限发电机。

from itertools import repeat
inputs = (get_input("Is this ok? (y/n)") for _ in repeat(None))
response = (i.lower()=="y" for i in inputs if i.lower() in ("y", "n"))

while True:
    #snip: print out current state
    if next(response):
        break
    #do more processing with menus and stuff

其他回答

将循环逻辑分解为迭代器,迭代器产生循环变量并在完成时返回——这里有一个简单的迭代器,它将图像按行/列排列,直到我们用完图像或找不到放置它们的位置:

def it(rows, cols, images):
    i = 0
    for r in xrange(rows):
        for c in xrange(cols):
            if i >= len(images):
                return
            yield r, c, images[i]
            i += 1 

for r, c, image in it(rows=4, cols=4, images=['a.jpg', 'b.jpg', 'c.jpg']):
    ... do something with r, c, image ...

这样做的优点是将复杂的循环逻辑和处理分开。

我个人会做的是使用一个boolean,当我准备跳出外部循环时切换。例如

while True:
    #snip: print out current state
    quit = False
    while True:
        ok = input("Is this ok? (y/n)")
        if ok.lower() == "y":
            quit = True
            break # this should work now :-)
        if ok.lower() == "n":
            quit = True
            break # This should work too :-)
    if quit:
        break
    #do more processing with menus and stuff

我的第一反应是将嵌套循环重构为一个函数,并使用return来跳出。

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   # <--- !

你可以使用一个标志来打破循环:

if found:
  break

这里,'found'是标志,你最初将它设置为False,然后在循环中使用这段代码。

found = False
for table_height in range(500):
  if found:
    break

下面是三个for循环的完整代码:

found = False
for table_height in range(500):
  if found:
    break
  for cat_height in range(500):
    if found:
      break

    for tort_height in range(500):
      equation1 = table_height + cat_height == tort_height + 170
      equation2 = table_height + tort_height == cat_height + 130
      if equation1 and equation2:
        print('table', table_height, '  cat', cat_height, '  tortoise', tort_height)
        found = True
        break

在这段代码中,如果等式1和等式2为True,它将设置'found'标志为True,并跳出最里面的for循环,它也将跳出其他两个for循环,因为'found'为True。