如何在 Python 中的嵌套循环中继续

How to continue in nested loops in Python

提问by James

How can you continuethe parent loop of say two nested loops in Python?

你怎么能continue在 Python 中说两个嵌套循环的父循环？

for a in b:
    for c in d:
        for e in f:
            if somecondition:
                <continue the for a in b loop?>

I know you can avoid this in the majority of cases but can it be done in Python?

我知道在大多数情况下您可以避免这种情况，但可以在 Python 中完成吗？

采纳答案by Duncan

1. Break from the inner loop (if there's nothing else after it)
2. Put the outer loop's body in a function and return from the function
3. Raise an exception and catch it at the outer level
4. Set a flag, break from the inner loop and test it at an outer level.
5. Refactor the code so you no longer have to do this.

1. 从内部循环中断（如果之后没有其他内容）
2. 将外循环的主体放在一个函数中并从该函数返回
3. 引发异常并在外层捕获它
4. 设置一个标志，中断内部循环并在外部级别对其进行测试。
5. 重构代码，这样您就不再需要这样做了。

I would go with 5 every time.

我每次都会带5个。

回答by Tony The Lion

You use breakto break out of the inner loop and continue with the parent

你break用来打破内部循环并继续使用父级

for a in b:
    for c in d:
        if somecondition:
            break # go back to parent loop

回答by Eric

Here's a bunch of hacky ways to do it:

这里有一堆hacky的方法来做到这一点：

1. Create a local function

   for a in b:
       def doWork():
           for c in d:
               for e in f:
                   if somecondition:
                       return # <continue the for a in b loop?>
       doWork()
   

   A better option would be to move doWork somewhere else and pass its state as arguments.

2. Use an exception

   class StopLookingForThings(Exception): pass
   
   for a in b:
       try:
           for c in d:
               for e in f:
                   if somecondition:
                       raise StopLookingForThings()
       except StopLookingForThings:
           pass
   

1. 创建本地函数

   for a in b:
       def doWork():
           for c in d:
               for e in f:
                   if somecondition:
                       return # <continue the for a in b loop?>
       doWork()
   

   更好的选择是将 doWork 移到其他地方并将其状态作为参数传递。

2. 使用异常

   class StopLookingForThings(Exception): pass
   
   for a in b:
       try:
           for c in d:
               for e in f:
                   if somecondition:
                       raise StopLookingForThings()
       except StopLookingForThings:
           pass
   

回答by John La Rooy

from itertools import product
for a in b:
    for c, e in product(d, f):
        if somecondition:
            break

回答by Samourai

use a boolean flag

使用布尔标志

problem = False
for a in b:
  for c in d:
    if problem:
      continue
    for e in f:
        if somecondition:
            problem = True