I'm try to do something like that in Python:

return None if a is None

Instead of having:

if a is None:return None

But I get an invalid syntax error.

I tried to use pass:

return None if a is None else pass

But it doesn't work as well. Is there a pythonian way to do it?

return None if ...

is unconditional return of a conditional value.

If you want conditional return, all what you can change is put it on single line, like that:

if a is None: return