问题
I use the following method to break the double loop in Python.
for word1 in buf1:
find = False
for word2 in buf2:
...
if res == res1:
print "BINGO " + word1 + ":" + word2
find = True
if find:
break
Is there a better way to break the double loop?
回答1:
Probably not what you are hoping for, but usually you would want to have a break after setting find to 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
Another way is to use a generator expression to squash the for into a single loop
for word1, word2 in ((w1, w2) for w1 in buf1 for w2 in buf2):
...
if res == res1:
print "BINGO " + word1 + ":" + word2
break
You may also consider using itertools.product
from itertools import product
for word1, word2 in product(buf1, buf2):
...
if res == res1:
print "BINGO " + word1 + ":" + word2
break
回答2:
The recommended way in Python for breaking nested loops is... Exception
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
回答3:
Most times you can use a number of methods to make a single loop that does the same thing as a double loop.
In your example, you can use itertools.product to replace your code snippet with
import itertools
for word1, word2 in itertools.product(buf1, buf2):
if word1 == word2:
print "BINGO " + word1 + ":" + word2
break
The other itertools functions are good for other patterns too.
回答4:
Refactor using functions so you can return when you find your "bingo".
The proposal to allow explicit breaking out of nested loops has been rejected: http://www.python.org/dev/peps/pep-3136/
来源：https://stackoverflow.com/questions/2597104/break-the-nested-double-loop-in-python