e.g., how can I find out that the executable has been installed in "/usr/bin/python" and the library files in "/usr/lib/python2.6"?
You want the sys module:
>>> print sys.executable
/usr/bin/python
>>> print sys.path
['', '/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python26.zip',
 '/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-darwin', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac/lib-scriptpackages', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-old', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload', 
'/Library/Python/2.6/site-packages', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/PyObjC', 
'/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/wx-2.8-mac-unicode']
Python: what package contains the installation metadata?