2.3.2 Reserved classes of identifiers

Certain classes of identifiers (besides keywords) have special meanings. These are:

Form Meaning
_* Not imported by "from module import *"
__*__ System-defined name
__* Class-private name mangling

Form	Meaning
`_*`	Not imported by "`from module import *`"
`__*__`	System-defined name
`__*`	Class-private name mangling

(XXX need section references here.)