Accessing Objective-C hidden _cmd argument from Python

Question

I've poked around at the PyObjC innards quite a bit trying to figure this out. Is it possible to access Objective-C's hidden SEL _cmd method argument when writing a Python method? It's got to be generated at some point, but I'm not sure if that point is one at which my Python code can get to it.

I was mostly interested in this in order to be able to make an easy PyObjC NSLog text macro:

def meth_(self, arg):
    NSLog(u"%s called" % _cmd)

although I have found other ways to do this kind of logging in Python (see Jeremy's answer), so at this point it's become curiosity about the PyObjC bridge.

Jeremy W. Sherman · Accepted Answer · 2011-05-12 22:07:21Z

3

Why not go about it by logging the name of the Python function, instead? Then you can apply a Python approach to getting the function name, like throwing an exception and munging around in the stack trace, as shown in this code snippet.

ETA: This code demonstrates the "better way" mentioned in the prior snippet as introduced in Python 2.1: using sys._getframe(). It is far simpler.

answered May 12, 2011 at 22:07

Jeremy W. Sherman

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1 Comment

jscs Over a year ago

Indeed. I've seen these and made use of the second when necessary. Not exactly what I'm looking for, but I appreciate the answer.

Cy-4AH · Accepted Answer · 2014-03-16 20:48:26Z

-1

I am not familiar with Python. But in objective-C instead _cmd you can find method selector by:

const id* selfPtr = &self;
SEL sel = *(SEL*)(void*)(--selfPtr);

May be you can use same approach in Python.

answered Mar 16, 2014 at 20:48

Cy-4AH

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