The following identifiers are used as reserved words, or keywords of the language, and cannot be used as ordinary identifiers. They must be spelled exactly as written here:
and del from not while as elif global or with assert else if pass yield break except import print class exec in raise continue finally is return def for lambda try
Changed in version 2.4: None became a constant and is now recognized by the compiler as a name for the built-in object None. Although it is not a keyword, you cannot assign a different object to it.
Changed in version 2.5:
Both as and with are only recognized
when the with_statement future feature has been enabled.
It will always be enabled in Python 2.6. See section 7.5 for
details. Note that using as and with as identifiers
will always issue a warning, even when the with_statement future
directive is not in effect.