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

解决方法有两种

举个例子:这两个矩阵相等/相同吗? 矩阵x1和矩阵x2是相同大小的,n,二维矩阵。

第一个解决方案,没有函数

same_matrices = True
inner_loop_broken_once = False
n = len(matrix1)

for i in range(n):
    for j in range(n):

        if matrix1[i][j] != matrix2[i][j]:
            same_matrices = False
            inner_loop_broken_once = True
            break

    if inner_loop_broken_once:
        break

第二个解决方案,用函数

这是我案子的最终解决方案。

def are_two_matrices_the_same (matrix1, matrix2):
    n = len(matrix1)
    for i in range(n):
        for j in range(n):
            if matrix1[i][j] != matrix2[i][j]:
                return False
    return True

其他回答

keeplooping = True
while keeplooping:
    # Do stuff
    while keeplooping:
          # Do some other stuff
          if finisheddoingstuff():
              keeplooping = False

或者类似的东西。

您可以在内部循环中设置一个变量,并在内部循环退出后立即在外部循环中检查它,如果合适的话可以中断。我有点喜欢GOTO方法,前提是你不介意使用愚人节的笑话模块——它不是python的,但它确实有意义。

在Python中有一个隐藏的技巧…Else结构,可以用来模拟双中断,而不需要太多的代码更改/添加。本质上,如果while条件为false,则触发else块。任何异常、continue或break都不会触发else块。有关更多信息,请参阅对“Python while语句上的Else子句”或Python while上的doc (v2.7)的回答。

while True:
    #snip: print out current state
    ok = ""
    while ok != "y" and ok != "n":
        ok = get_input("Is this ok? (y/n)")
        if ok == "n" or ok == "N":
            break    # Breaks out of inner loop, skipping else

    else:
        break        # Breaks out of outer loop

    #do more processing with menus and stuff

唯一的缺点是需要将双中断条件移到while条件中(或添加一个标志变量)。对于for循环也存在这种变化,其中else块在循环完成后被触发。

希望这能有所帮助:

x = True
y = True
while x == True:
    while y == True:
         ok = get_input("Is this ok? (y/n)") 
         if ok == "y" or ok == "Y":
             x,y = False,False #breaks from both loops
         if ok == "n" or ok == "N": 
             break #breaks from just one
# this version breaks up to a certain label

break_label = None
while True:
    # snip: print out current state
    while True:
        ok = get_input("Is this ok? (y/n)")
        if ok == "y" or ok == "Y":
            break_label = "outer"   # specify label to break to
            break
        if ok == "n" or ok == "N":
            break
    if break_label:
        if break_label != "inner":
            break                   # propagate up
        break_label = None          # we have arrived!
if break_label:
    if break_label != "outer":
        break                       # propagate up
    break_label = None              # we have arrived!

#do more processing with menus and stuff

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