如果内部循环内的条件为真，则几个嵌套的'for'循环继续下一次外循环迭代

Question

I know it is terribly inefficient and ugly code, but if I have three for loops, nested inside each other such as so:

for x in range(0, 10):
    for y in range(x+1, 11):
       for z in range(y+1, 11):
           if ...

I want to break the two inner loops and continue to the next iteration of the outer loop if the if statement is true. Can this be done?

Answer 1

Check some variable after each loops ends:

for x in range(0, 10):
    for y in range(x+1, 11):
        for z in range(y+1, 11):
            if condition:
                variable = True
                break
            #...
        if variable:
            break;
        #...

Answer 2

Another option is to use exceptions instead of state variables:

class BreakException(Exception):
    pass

for x in range(0, 10):
    try:
        for y in range(x+1, 11):
           for z in range(y+1, 11):
               if True:
                   raise BreakException
    except BreakException:
        pass

I imagine this could be especially useful if bailing out of more than two inner loops.

Answer 3

n = False
for x in range(0,10):
    if n == True:
        print(x,y,z)
    for y in range(x+1, 11):
        if n == True:
            break
        for z in range(y+1, 11):
            if z == 5:
                n = True
                break

(1, 2, 5)
(2, 2, 5)
(3, 3, 5)
(4, 4, 5)
(5, 5, 5)
(6, 6, 5)
(7, 7, 5)
(8, 8, 5)
(9, 9, 5)

Answer 4

A possible solution is to merge the two inner loops to a single one (that can be terminated with break ):

import itertools

for x in range(10):
    for y, z in itertools.combinations(range(x+1, 11), 2):
        if condition:
            break