Python how to get the calling function (not just its name)?

Calling can happen from any code object (and from an extension module/builtin): from exec, execfile, from module name space (during import), from within a class definition, from within a method / classmethod / staticmethod, from a decorated function/method, from within a nested function, … – so there is no “calling function” in general, and the difficulty to do anything good with that.

The stack frames and their code objects are the most general you can get – and examine the attributes.

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This one finds the calling function in many cases:

import sys, inspect

def get_calling_function():
    """finds the calling function in many decent cases."""
    fr = sys._getframe(1)   # inspect.stack()[1][0]
    co = fr.f_code
    for get in (
        lambda:fr.f_globals[co.co_name],
        lambda:getattr(fr.f_locals['self'], co.co_name),
        lambda:getattr(fr.f_locals['cls'], co.co_name),
        lambda:fr.f_back.f_locals[co.co_name], # nested
        lambda:fr.f_back.f_locals['func'],  # decorators
        lambda:fr.f_back.f_locals['meth'],
        lambda:fr.f_back.f_locals['f'],
        ):
        try:
            func = get()
        except (KeyError, AttributeError):
            pass
        else:
            if func.__code__ == co:
                return func
    raise AttributeError("func not found")
     
# Usage

def f():
    def nested_func():
        print get_calling_function()
    print get_calling_function()
    nested_func()

class Y:
    def meth(self, a, b=10, c=11):
        print get_calling_function()
        class Z:
            def methz(self):
                print get_calling_function()
        z = Z()
        z.methz()
        return z
    @classmethod
    def clsmeth(cls):
        print get_calling_function()
    @staticmethod
    def staticmeth():
        print get_calling_function()

f()
y = Y()
z = y.meth(7)
z.methz()
y.clsmeth()
##y.staticmeth()  # would fail

It finds:

<function f at 0x012E5670>
<function nested_func at 0x012E51F0>
<bound method Y.meth of <__main__.Y instance at 0x01E41580>>
<bound method Z.methz of <__main__.Z instance at 0x01E63EE0>>
<bound method Z.methz of <__main__.Z instance at 0x01E63EE0>>
<bound method classobj.clsmeth of <class __main__.Y at 0x01F3CF10>>

However, it may fail to find the function, or find the wrong function, for example, finding the wrong decorator-generated wrapper when the same decorator is used on multiple functions with the same name in different scopes.