Break the nested (double) loop in Python

python nested-loops
prosseek picture prosseek · Apr 8, 2010 · Viewed 66.4k times · Source

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?

Answer

John La Rooy picture John La Rooy · Apr 8, 2010

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

Related questions

How to break out of multiple loops?

Given the following code (that doesn't work): 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 …

Read More
Breaking out of nested loops

Is there an easier way to break out of nested loops than throwing an exception? (In Perl, you can give labels to each loop and at least continue an outer loop.) for x in range(10): for y in range(10): print …

Read More
Single Line Nested For Loops

Wrote this function in python that transposes a matrix: def transpose(m): height = len(m) width = len(m[0]) return [ [ m[i][j] for i in range(0, height) ] for j in range(0, width) ] In the process I realized I don't fully …

Read More