2.3.2 Reserved classes of identifiersCertain classes of identifiers (besides keywords) have specialmeanings. These classes are identified by the patterns of leading andtrailing underscore characters:- Not imported by "from module import *". The specialidentifier "_" is used in the interactive interpreter to storethe result of the last evaluation; it is stored in the__builtin__ module. When not in interactive mode, "_" has no special meaning and is not defined. See section 6.12, ``The import statement.'' The name "_" is often used in conjunction withinternationalization; refer to the documentation for thegettext module for moreinformation on this convention.- System-defined names. These names are defined by the interpreterand its implementation (including the standard library);applications should not expect to define additional names using thisconvention. The set of names of this class defined by Python may beextended in future versions. See section 3.4, ``Special method names.''- Class-private names. Names in this category, when used within thecontext of a class definition, are re-written to use a mangled formto help avoid name clashes between ``private'' attributes of baseand derived classes. See section 5.2.1, ``Identifiers (Names).'' See About this document... for information on suggesting changes.