How to break out from multiple loops python?

In this Python tutorial, you will learn how to break out of multiple loops in Python.

Agenda

Let’s dive into the tutorial.

Introduction

We have to stop at some point in a looping statements. Based on the condition or requirement in the application, we have to come out of the loop. In python, we can do this by using break and return keywords.

Let’s study it in detail.

break:

The break is a keyword in python and it used to break out from a loop. It will stop the execution of looping statements based on the condition specified under a loop.

return:

The return is a keyword in python used to break out from the function. It is used only with functions. Based on the condition, it will return the result and terminate working of the function. The main thing is that we have to provide for loop within the function.

Break out from multiple for loops using break

Here, we will use nested for loops and specify the condition to break using the if statement. So based on the condition, we are going to break from both the for loops.

Syntax:

for iterator1 in iterable/range(sequence):
    for iterator2 in iterable/range(sequence):
    ...............
    ...............
        for iteratorn in iterable/range(sequence):
        conditional-statements
            break from all loops
other statements
...............
...............

Here, an iterator is used to iterate the looping statements and conditional statements refer to if-else, etc. We need to break the loops by checking conditions.

Let’ ‘s see a few examples to understand it better.

Example 1:

In this example, we are using two for loops to iterate two lists of integer elements and break the loops if the sum of two iterators is greater than or equal to 10. Otherwise, we are displaying the two iterators.

#create list of 5 integers
list1=[6,7,8,9,10]

#create list of 3 integers
list2=[2,4,6]

breakFlag = False
#iterate first list
for iterator1 in list1:
    #iterate second list
    for iterator2 in list2:
        #check if sum of two iterators is greater than  or equal to 10
        if(iterator1+iterator2>=10):
            # break the loop
            breakFlag = True
            break
        else:
            #display iterators
            print(iterator1,iterator2)
    #break first loop
    if breakFlag:
        break     

Output:

6 2

The first list has 5 integers, and the second list has 3 integers. We created a variable breakFlag which is initialied to False. We can see that if the sum of two iterators is greater than or equal to 10, it goes inside if condition and breaks the second or inside loop by executing the break statement. So again we are checking the breakFlag status, if it is True, then we are breaking the first loop. In other cases, it goes inside else block and displays the iterators.

We can also use the break inside the function. Let’ ‘s see the same example to understand it better.

Example 2:

# Create a function named - my_ownfunction
def my_ownfunction():
    #create list of 5 integers
    list1=[6,7,8,9,10]

    #create list of 3 integers
    list2=[2,4,6]

    breakFlag = False
    #iterate first list
    for iterator1 in list1:
        #iterate second list
        for iterator2 in list2:
            # check if sum of two iterators is 
            # greater than  or equal to 10
            if(iterator1+iterator2>=10):
                # break the nested loop
                breakFlag = True
                break
            else:
                # display iterators
                print(iterator1,iterator2)
        # break the first loop
        if breakFlag:
            break 

# call the function
my_ownfunction()

Output:

6 2

It is the same as the first example, but we have written all the code inside the function named – my_ownfunction() and called it.

Break out from multiple for loops using return keyword

The return keyword can be used within functions. It returns a value and will skip the statements after the return statement. We can also say that it is used to exit a function.

Syntax:

def function_name():
    for iterator1 in iterable/range(sequence):
        for iterator2 in iterable/range(sequence):
            ...............
            ...............
            for iteratorn in iterable/range(sequence):
                conditional-statements
                return

function_name()
other statements
...............
...............

where function_name() is the name of the function and at last we have to call the function by its name.

Example 1:

In this example, we are using two for loops to iterate two lists of integer elements and break the loops by returning the sum of the first iteration.

def my_ownfunction():
    #create list of 5 integers
    list1=[6,7,8,9,10]

    #create list of 3 integers
    list2=[2,4,6]

    #iterate first list
    for iterator1 in list1:
        #iterate second list
        for iterator2 in list2:
            #return the sum of first iteration
            return iterator1 + iterator2

#call the function           
value = my_ownfunction()

print(value)      

Output:

8

From the above code, we have seen that the first 6 from the first list and 2 from the second list are iterated. The sum of 6 and 2 is 8 and we are returning this.

Example 2:

In this example, we are using two for loops to iterate two lists of integer elements and break the loops by checking the condition that the sum of two iterators that are greater than 8.

def my_ownfunction():
    #create list of 5 integers
    list1=[6,7,8,9,10]

    #create list of 3 integers
    list2=[2,4,6]

    #iterate first list
    for iterator1 in list1:
        #iterate second list
        for iterator2 in list2:
            # If sum of both the numbers is greater than 8
            # then exit from both the loops and return from function
            if iterator1 + iterator2 > 8:
                return iterator1 + iterator2

#call the function           
value = my_ownfunction()

print(value)

Output:

From the above code, we have seen that the first 6 from the first list and 4 from the second list are iterated, so the sum of 6 and 4 is 10. Hence the condition satisfies which is greater than 8. so it is returned the and broke both the loops.

Summary

If you want to break out from multiple loops in a function, you can use return as well as break. If your application doesn’t contain any function and you want to break out from multiple loops, you can use the break keyword. But make sure that return is used only with in the function.