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Document nonlocal statement. Written for GHOP by "Canadabear".

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Georg Brandl 2007-12-04 18:11:03 +00:00
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Doc/reference/simple_stmts.rst
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@ -765,12 +765,42 @@ The :keyword:`nonlocal` statement
.. productionlist::
nonlocal_stmt: "nonlocal" `identifier` ("," `identifier`)*
XXX: To be documented.
.. XXX add when implemented
: ["=" (`target_list` "=")+ `expression_list`]
: | "nonlocal" `identifier` `augop` `expression_list`
The :keyword:`nonlocal` statement causes the listed identifiers to refer to
previously bound variables in the nearest enclosing scope. This is important
because the default behavior for binding is to search the local namespace
first. The statement allows encapsulated code to rebind variables outside of
the local scope besides the global (module) scope.
.. note::
The outer scope for :keyword:`nonlocal` statements cannot be the module
scope.
.. XXX not implemented
The :keyword:`nonlocal` statement may prepend an assignment or augmented
assignment, but not an expression.
Names listed in a :keyword:`nonlocal` statement, unlike to those listed in a
:keyword:`global` statement, must refer to pre-existing bindings in an
enclosing scope (the scope in which a new binding should be created cannot
be determined unambiguously).
Names listed in a :keyword:`nonlocal` statement must not collide with
pre-existing bindings in the local scope.
.. seealso::
:pep:`3104` - Access to Names in Outer Scopes
The specification for the :keyword:`nonlocal` statement.
.. rubric:: Footnotes
.. [#] It may occur within an :keyword:`except` or :keyword:`else` clause. The
restriction on occurring in the :keyword:`try` clause is implementor's laziness
and will eventually be lifted.
restriction on occurring in the :keyword:`try` clause is implementor's
laziness and will eventually be lifted.