打破Python中的嵌套(双)循环

Question

我使用以下方法来破坏Python中的双循环.

for word1 in buf1:
    find = False
    for word2 in buf2:
        ...
        if res == res1:
            print "BINGO " + word1 + ":" + word2
            find = True
    if find:
        break

有没有更好的方法来打破双循环？

Answer 1

也许不是你所希望的,但通常你会希望有一个break设置后find,以True

for word1 in buf1: 
    find = False 
    for word2 in buf2: 
        ... 
        if res == res1: 
            print "BINGO " + word1 + ":" + word2 
            find = True 
            break             # <-- break here too
    if find: 
        break 

另一种方法是使用生成器表达式将其压缩for成单个循环

for word1, word2 in ((w1, w2) for w1 in buf1 for w2 in buf2):
    ... 
    if res == res1: 
        print "BINGO " + word1 + ":" + word2
        break 

您也可以考虑使用 itertools.product

from itertools import product
for word1, word2 in product(buf1, buf2):
    ... 
    if res == res1: 
        print "BINGO " + word1 + ":" + word2
        break 

Answer 2

Python中用于破坏嵌套循环的推荐方法是......异常

class Found(Exception): pass
try:
    for i in range(100):
        for j in range(1000):
            for k in range(10000):
               if i + j + k == 777:
                  raise Found
except Found:
    print i, j, k 

Answer 3

大多数情况下,您可以使用多种方法来创建一个与双循环相同的循环.

在您的示例中,您可以使用itertools.product替换您的代码段

import itertools
for word1, word2 in itertools.product(buf1, buf2):
    if word1 == word2:
        print "BINGO " + word1 + ":" + word2
        break

其他itertools函数也适用于其他模式.

Answer 4

重构使用函数,以便在找到"宾果游戏"时返回.

允许显式中断嵌套循环的提议已被拒绝:http: //www.python.org/dev/peps/pep-3136/