what's the diff btw 'empty return' and 'return None'?

Question

i was implementing merge sort and in the base case found that there is no diff btw empty return and return None.

if cond:
   return

and

if cond:
   return None

is there any diff or 2 are equivalent?

They are equivalent. I tend to use an explicit `return None` if the function may return different types. — snakecharmerb, Feb 29 '20 at 19:50
For the caller of the function - they are the same. But for anyone reading the code, it's a matter of explicit vs implicit. — rdas, Feb 29 '20 at 19:51
There is also a difference in Python 2, if the function is a generator (i.e. has `yield` inside) - in that case `return` is a valid way to end the function whereas `return None` is not. — zvone, Feb 29 '20 at 19:54
PEP recommends `return None` if any valid value is returned elsewhere in the function, otherwise `return` is fine. — Carcigenicate, Feb 29 '20 at 19:54
"The `return` statement returns with a value from a function. `return` without an expression argument returns `None`. Falling off the end of a function also returns `None`." (from the [Official Python Tutorial](https://docs.python.org/3/tutorial/controlflow.html#defining-functions) — Jongware, Feb 29 '20 at 19:57

score 3 · Accepted Answer · answered Feb 29 '20 at 19:55

According to the doc, if no expression is given to return then None is substituted. So no there is no difference.

Edit:

Even with no return statement, a function returns None:

>>> def f():
...    print("do nothing")
...
>>> r=f()
do nothing
>>> r is None
True

1 Answers1