Why is break statement not working in this situation (python)?

Question

I have two lists:

list1 = [0,1,2,3,4,5]
list2 = [6,7,8,9,10,11]

and I want to add List2 to List1 until we find the first sum that is larger than 10, print out the summation, and stops.

My code is:

for val1 in list1: 
   for val2 in list2:
      if val1+val2 > 10 :
        print (val1, val2, val1 + val2)
        break
      else:
        continue

But the result is:

How to make the loop stops at the first sum? many thanks. Note: I want to maintain the for...if loop structure.

Firefighting Physicist · Answer 1 · 2022-03-30T06:11:02.473

1

Your 'break' statement only breaks out of the first (EDIT: innermost) loop. Put it into a function and return a value like so:

def foo(list1, list2):
    for val1 in list1: 
        for val2 in list2:
            if val1+val2 > 10 :
                print (val1, val2, val1 + val2)
                return (val1 + val2) # or whatever you are interested in
            else:
                continue

edited Mar 30 '22 at 06:11

answered Mar 30 '22 at 06:00

Firefighting Physicist

363
2
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1

*only breaks out of the first loop* -- really? i always thought it breaks the **nearst** loop. – Lei Yang Mar 30 '22 at 06:10
@leiyang return does exit the function in any case returning whatever objects listed in its statement. – jlandercy Mar 30 '22 at 06:12
you are correct, that was phrased badly. The 'first' loop that it can break out of, which is the nearest/innermost, but not the first one when reading the code. Thanks for the correction, I edited the post! – Firefighting Physicist Mar 30 '22 at 06:13
Nice answer, this works. thanks! – Danny Mar 30 '22 at 06:22
@Danny: You can accept an answer as well – Firefighting Physicist Mar 30 '22 at 07:11

score 0 · Answer 2 · answered Mar 30 '22 at 05:59

0

break keyword is used to break out of only one loop to break out of multiple loop use _break boolean variable initially which is False

list1 = [0,1,2,3,4,5]
list2 = [6,7,8,9,10,11]

_break = False

for val1 in list1: 
   for val2 in list2:
      if val1+val2 > 10 :
        print (val1, val2, val1 + val2)
        _break = True
        if _break:
         break
   if _break:
       break

Output:

0 11 11

answered Mar 30 '22 at 05:59

Udesh

2,415
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Why not setting the variable equal to the predicate that breaks the loop. – jlandercy Mar 30 '22 at 06:07

score 0 · Answer 3 · answered Mar 30 '22 at 06:05

0

Just maintain a flag variable to break out of the outer loop.

list1 = [0,1,2,3,4,5]
list2 = [6,7,8,9,10,11]
flag=0
for val1 in list1: 
    for val2 in list2:
        if val1+val2 > 10 :
            print (val1, val2, val1 + val2)
            flag=1
            break
        else:
            continue
    if(flag):
        break

If you don't have anything to execute after this, you can use exit() method to terminate the code.

list1 = [0,1,2,3,4,5]
list2 = [6,7,8,9,10,11]
for val1 in list1: 
    for val2 in list2:
        if val1+val2 > 10 :
            print (val1, val2, val1 + val2)
            exit()
        else:
            continue

answered Mar 30 '22 at 06:05

Ponprabhakar S

1
1

Why not setting the variable equal to the predicate that breaks the loop. what does your answer add to the previous stating the same hack. – jlandercy Mar 30 '22 at 06:09
'Why not setting the variable equal to the predicate that breaks the loop' -> I can't get you. 'what does your answer add to the previous stating the same hack.' -> There are many to solve a problem, its a coincidence. – Ponprabhakar S Mar 30 '22 at 06:16
`Flag = val1+val2 > 10` will do the job as well and makes the logic connected to the predicate instead of having a constant added and disconnected from the logic. Anyway adding this constant is a bit hackish and is probably not the proper way to reach the goal. – jlandercy Mar 30 '22 at 06:20
The first answer works for me. Thanks! – Danny Mar 30 '22 at 06:22

score 0 · Answer 4 · answered Mar 30 '22 at 06:20

It's just breaking the inner loop. If you want break both for loop then, You can use flag.

list1 = [0,1,2,3,4,5]
list2 = [6,7,8,9,10,11]
flag = 0
for val1 in list1: 
    for val2 in list2:
        if val1+val2 > 10 :
            print(val1, val2, val1 + val2)
            flag = 1
            break
        else:
            continue
     if flag:
         break

Why is break statement not working in this situation (python)?

4 Answers4

Output: