Question

How I can get the number of elements returned from a function whithout execute it ? And may be also, know the type of these elements ?

I know i can do something like :

def foo ():
    return 'a', 2

handle = foo()
print len(handle)
>> 2

But here i need to execute my function …

Answer 1

You can’t — A function can return different numbers of arguments (stored in a single tuple) and different types of variables in that tuple depending on input or other factors. consider the (silly) function:

def foo(arg):
    if arg:
       return 1,2
    else
       return "foo","bar","baz"

Now call it:

foo(1) # (1,2)
foo(0) # ("foo","bar","baz")

The only way to know what a function will return is to 1) read the source or 2) (If you’re a trusting sort of person) read the documentation for the function :-).