How can a function access its own attributes?

Question

is it possible to access the python function object attributes from within the function scope?

e.g. let\'s have

def f():
    return          


        

Answer 1

Well, let's look at what function is:

>>> def foo():
...     return x
... 
>>> foo.x = 777
>>> foo.x
777
>>> foo()
Traceback (most recent call last):
  File "", line 1, in 
  File "", line 2, in foo
NameError: global name 'x' is not defined
>>> dir(foo)
['__call__', '__class__', '__delattr__', '__dict__', '__doc__', '__get__', 
'__getattribute__', '__hash__', '__init__', '__module__', '__name__', '__new__', 
'__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__str__', 
'func_closure', 'func_code', 'func_defaults', 'func_dict', 'func_doc', 
'func_globals', 'func_name', 'x']
>>> getattr(foo, 'x')
777

Aha! So the attribute was added to the function object but it won't see it because it is looking for global x instead.

We can try to grab the frame of the function execution and try to look what's there (essentially what Anthony Kong suggested but w/o inspect module):

>>> def foo():
...     import sys
...     return sys._getframe()
... 
>>> fr = foo()
>>> dir(fr)
['__class__', '__delattr__', '__doc__', '__getattribute__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__str__', 'f_back', 'f_builtins', 'f_code', 'f_exc_traceback', 'f_exc_type', 'f_exc_value', 'f_globals', 'f_lasti', 'f_lineno', 'f_locals', 'f_restricted', 'f_trace']
>>> fr.f_locals
{'sys': }
>>> fr.f_code
", line 1>
>>> fr.f_code.co_code
'd\x01\x00d\x00\x00k\x00\x00}\x00\x00|\x00\x00i\x01\x00\x83\x00\x00S'
>>> fr.f_code.co_name
'foo'

Aha! So maybe we can get the name of the function from the name of the code block and then look in round-about way for the attribute? Sure enough:

>>> getattr(fr.f_globals[fr.f_code.co_name], 'x')
777
>>> fr.f_globals[fr.f_code.co_name].x
777
>>> def foo():
...     import sys
...     frm = sys._getframe()
...     return frm.f_globals[frm.f_code.co_name].x
... 
>>> foo.x=777
>>> foo()
777

That's great! But would it stand the renaming and deletion of original function?

>>> g = foo
>>> g.func_name
'foo'
>>> g.func_code.co_name
'foo'

Ah, very doubtful. The function object and its code object still insist they are called foo. Sure enough, here is where it breaks:

>>> g.x
777
>>> g.x=888
>>> foo.x
888
>>> g()
888
>>> del foo
>>> g()
Traceback (most recent call last):
  File "", line 1, in 
  File "", line 4, in foo
KeyError: 'foo'

Dang! So in general it can't be done through introspection via the execution frames. The problems seems to be that there is a difference between function object and code object - code objects are what is executed and is just one attribute func_code of the function-object and as such has no access to the func_dict attribute, where our attribute x is:

>>> g

>>> type(g)

>>> g.func_code
", line 1>
>>> type(g.func_code)

>>> g.func_dict
{'x': 888}

There is of course other chicanery you can do so that it seems as function - in particular the trick with class definition... but that is not a function per se. It all depends on what do you really need to do with that.