[Tut] What’s the Difference Between return and break in Python?

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What’s the Difference Between return and break in Python?

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Question: What is the difference between

Code:

return

and

Code:

break

? When to use which?

Let’s first look at a short answer before we dive into a simple example to understand the differences and similarities between

Code:

return

and

Code:

break

.

Comparison



Both

Code:

return

and

Code:

break

are keywords in Python.

• The keyword
  Code:

  return
  ends a function and passes a value to the caller.
  
  
• The keyword
  Code:

  break
  ends a loop immediately without doing anything else. It can be used within or outside a function.
  

Code:

return

|

Code:

break

Used to end a function |
Used to end a

Code:

for

or

Code:

while

loop

Passes an optional value to the caller of the function (e.g.,

Code:

return 'hello'

) |
Doesn’t pass anything to the “outside”

While they serve a different purpose, i.e., ending a function vs ending a loop, there are some cases where they can be used interchangeably.

Similar Use Cases

The following use case shows why you may have confused both keywords

Code:

return

and

Code:

break

. In both cases, you can use them to end a loop inside a function and return to the outside.

Here’s the variant using

Code:

return

:

Code:

def f(): for i in range(10): print(i) if i>3: return f()

And here’s the variant using

Code:

break

:

Code:

def f(): for i in range(10): print(i) if i>3: break f()

Both code snippets do exactly the same—printing out the first 5 values 0, 1, 2, 3, and 4.

Output:

Code:

0 1 2 3 4

However, this is where the similarity between those two keywords ends. Let’s dive into a more common use case where they both perform different tasks in the code.

Different Use Cases

The following example uses both keywords

Code:

break

and

Code:

return

. It uses the keyword

Code:

break

to end the loop as soon as the loop variable

Code:

i

is greater than 3.

So the line

Code:

print(i)

is never executed after variable

Code:

i

reaches the value 4—the loop ends.

But the function doesn’t end because

Code:

break

only ends the loop and not the function. That’s why the statement

Code:

print('hi')

is still executed, and the return value of the function is

Code:

42

(which we also print in the final line).

Code:

def f(): for i in range(10): if i>3: break print(i) print('hi') return 42 print(f())

Output:

Code:

0 1 2 3 hi 42

Summary

The keyword

Code:

return

is different and more powerful than the keyword

Code:

break

because it allows you to specify an optional return value. But it can only be used in a function context and not outside a function.

• You use the keyword
  Code:

  return
  to give back a value to the caller of the function or terminate the whole function.
  
  
• You use the keyword
  Code:

  break
  to immediately stop a
  Code:

  for
  or
  Code:

  while
  loop.
  

Rule: Only if you want to exit a loop inside a function and this would also exit the whole function, you can use both keywords. In that case, I’d recommend using the keyword

Code:

return

instead of

Code:

break

because it gives you more degrees of freedom, i.e., specifying the return value. Plus, it is more explicit which improves the readability of the code.

Thanks for reading over the whole tutorial—if you want to keep learning, feel free to join my email academy. It’s fun!

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