##
2.3.2 Reserved classes of identifiers

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

Form | Meaning | Notes
--- | --- | ---
`_*` | Not imported by "`from module import *`" | (1)
`__*__` | System-defined name |
`__*` | Class-private name mangling |

See sections: 6.12, ``The `import` statement''; 3.3, ``Special method names''; 5.2.1, ``Identifiers (Names)''.

Note:

(1)
  The special identifier "`_`" is used in the interactive interpreter to store the 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.