Cameron Laird's personal notes on introspection in Python

In Usenet article <199803021544.KAA17164@eric.CNRI.Reston.Va.US>, Guido followed up

Good question. Python has a lot of introspection features but some of them are a bit haphazard and others are perhaps less-than-optimally documented.
(The key ones, of course, are so simple that you don't even think about them -- __dict__, __class__, __bases__, __name__, __file__, as well as locals(), globals(), vars(), dir(), type(), isinstance(), issubclass(), not to mention sys.modules.)
I've rarely felt the need to extract signatures from functions, but I can see that such a need exists in others.
Perhaps we can create a list of needed introspection features?

That's what this page is: "a list of needed introspection features". The initial question had to do with a function which reports a method's signature. Fred L. Drake, Jr., pointed out a number of features beyond those Guido mentions above, including:

compile()'s access to the Python parser
While Guido writes "... not to mention sys.modules", CL thanks Fred for pointing out sys.version, sys.name (sometimes os.uname()), and sys.executable in particular.

[explain]

        You could try:
        
        	try:
        	    version = func.func_globals['__version__']
        	except KeyError:
        	    version = None
        
          The value of __version__ should be set if the author will make sure
        the module will not be released without updating the number.  One way
        to do this under CVS or RCS would be:
        
        	__version__ = "$Revision$"
        
          Other revision control systems may support similar constructs.

Other possibilities that come to mind quickly (disclaimer: I'm writing this list in creative mode; it's likely that several of them are already implemented, and I just haven't noticed it yet):

a function to report a method's textual implementation (or bytecode?)
a function to report formal arguments' defaults
miscellaneous security-related data, including particularly counts of evaluations (valuable for accounting and denial-of-service considerations)
OS dependences:
- template for formation of name of shared-library extension
- filename munging (already available ...)

Cameron Laird's personal notes on introspection in Python/claird@phaseit.net