How to get function string name from i-th stack position?

[dmitrey]

On Dec 30, 11:48 pm, Ian Kelly <ian.g.ke... at gmail.com> wrote:
> On Fri, Dec 30, 2011 at 11:43 AM, dmitrey <dmitre... at gmail.com> wrote:
> > Thank you. And what should I do to get function by itself instead of
> > its string name, e.g. I want to know does this function is my_func or
> > any other? For example, I would like to check is this function Python
> > sum(), or maybe numpy.sum(), or anything else?
>
> The Python stack only includes Python code objects.  Built-ins like
> sum won't appear in it because they're basically C functions and don't
> have associated code objects.  If you really want to see them, you
> could probably do something with ctypes to inspect the C stack, but I
> don't recommend it.
>
> You can get the Python code objects from the stack by calling
> inspect.stack(), which includes each frame object currently on the
> stack as the first member of each tuple.  E.g.:
>
> frames = map(operator.itemgetter(0), inspect.stack())
>
> Each frame has an f_code attribute that stores the code object
> associated with that frame.  Getting the actual function from the code
> object is tricky, for two reasons.  One, not all code objects
> represent functions.  There are also code objects for modules, class
> definitions, and probably other thing as well.  Two, code objects
> don't have associated functions. The relationship is the reverse:
> functions have associated code objects.  You would have to iterate
> over each function that you're interested in, looking for one with a
> func_code attribute that "is" the frame's f_code attribute.
>
> In any case, testing function identity is a rather large rabbit hole
> that is best avoided.  These are mathematically the same function:
>
> def plus1(value):
>     return value + 1
>
> plus_one = lambda x: x + 1
>
> But they are two distinct function objects, and there is no way
> programmatically to determine that they are the same function except
> by comparing the bytecode (which won't work generally because of the
> halting problem).
>
> What is it that you're trying to do?  Perhaps the helpful folks on the
> list will be able to suggest a better solution if you can provide more
> details.
>
> Cheers,
> Ian

Maybe it is somehow possible to compare function id with my candidates
id, e.g.
PythonSumID = id(sum)
import numpy
NumpySumID = id(numpy.sum)
func = getting_function_from_Nth_stack_level_above
if id(func) == PythonSumID:
 ....
elif id(func) == NumpySumID:
 ....
else:
 ....
I need it due to the following reason: FuncDesigner users often use
Python or numpy sum on FuncDesigner objects, while FuncDesigner.sum()
is optimized for this case, works faster and doesn't lead to "Max
recursion dept exceeded", that sometimes trigger for numpy or Python
sum() when number of summarized elements is more than several
hundreds. I would like to print warning "you'd better use FuncDesigner
sum" if this case has been identified.
Regards, D.