diff options
Diffstat (limited to 'Doc/reference')
| -rw-r--r-- | Doc/reference/compound_stmts.rst | 25 | ||||
| -rw-r--r-- | Doc/reference/simple_stmts.rst | 15 |
2 files changed, 28 insertions, 12 deletions
diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst index dca9362..d7792f1 100644 --- a/Doc/reference/compound_stmts.rst +++ b/Doc/reference/compound_stmts.rst @@ -559,12 +559,14 @@ Parameters may have annotations of the form "``: expression``" following the parameter name. Any parameter may have an annotation even those of the form ``*identifier`` or ``**identifier``. Functions may have "return" annotation of the form "``-> expression``" after the parameter list. These annotations can be -any valid Python expression and are evaluated when the function definition is -executed. Annotations may be evaluated in a different order than they appear in -the source code. The presence of annotations does not change the semantics of a -function. The annotation values are available as values of a dictionary keyed -by the parameters' names in the :attr:`__annotations__` attribute of the -function object. +any valid Python expression. The presence of annotations does not change the +semantics of a function. The annotation values are available as values of +a dictionary keyed by the parameters' names in the :attr:`__annotations__` +attribute of the function object. If the ``annotations`` import from +:mod:`__future__` is used, annotations are preserved as strings at runtime which +enables postponed evaluation. Otherwise, they are evaluated when the function +definition is executed. In this case annotations may be evaluated in +a different order than they appear in the source code. .. index:: pair: lambda; expression @@ -587,6 +589,17 @@ access the local variables of the function containing the def. See section :pep:`3107` - Function Annotations The original specification for function annotations. + :pep:`484` - Type Hints + Definition of a standard meaning for annotations: type hints. + + :pep:`526` - Syntax for Variable Annotations + Ability to type hint variable declarations, including class + variables and instance variables + + :pep:`563` - Postponed Evaluation of Annotations + Support for forward references within annotations by preserving + annotations in a string form at runtime instead of eager evaluation. + .. _class: diff --git a/Doc/reference/simple_stmts.rst b/Doc/reference/simple_stmts.rst index 8d17383..ef9a5f0 100644 --- a/Doc/reference/simple_stmts.rst +++ b/Doc/reference/simple_stmts.rst @@ -853,12 +853,15 @@ can appear before a future statement are: * blank lines, and * other future statements. -.. XXX change this if future is cleaned out - -The features recognized by Python 3.0 are ``absolute_import``, ``division``, -``generators``, ``unicode_literals``, ``print_function``, ``nested_scopes`` and -``with_statement``. They are all redundant because they are always enabled, and -only kept for backwards compatibility. +The only feature in Python 3.7 that requires using the future statement is +``annotations``. + +All historical features enabled by the future statement are still recognized +by Python 3. The list includes ``absolute_import``, ``division``, +``generators``, ``generator_stop``, ``unicode_literals``, +``print_function``, ``nested_scopes`` and ``with_statement``. They are +all redundant because they are always enabled, and only kept for +backwards compatibility. A future statement is recognized and treated specially at compile time: Changes to the semantics of core constructs are often implemented by generating |