[Python-checkins] cpython (merge 3.2 -> 3.3): Merge issue #14893: Add function annotation example to function tutorial.
andrew.svetlov
python-checkins at python.org
Thu Nov 1 20:28:53 CET 2012
http://hg.python.org/cpython/rev/45167091b5f9
changeset: 80166:45167091b5f9
branch: 3.3
parent: 80162:717660ec8f67
parent: 80165:2bf99322218f
user: Andrew Svetlov <andrew.svetlov at gmail.com>
date: Thu Nov 01 21:27:23 2012 +0200
summary:
Merge issue #14893: Add function annotation example to function tutorial.
Patch by Zachary Ware.
files:
Doc/tutorial/controlflow.rst | 34 ++++++++++++++++++++++++
1 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/Doc/tutorial/controlflow.rst b/Doc/tutorial/controlflow.rst
--- a/Doc/tutorial/controlflow.rst
+++ b/Doc/tutorial/controlflow.rst
@@ -656,6 +656,40 @@
No, really, it doesn't do anything.
+.. _tut-annotations:
+
+Function Annotations
+--------------------
+
+.. sectionauthor:: Zachary Ware <zachary.ware at gmail.com>
+.. index::
+ pair: function; annotations
+ single: -> (return annotation assignment)
+
+:ref:`Function annotations <function>` are completely optional,
+arbitrary metadata information about user-defined functions. Neither Python
+itself nor the standard library use function annotations in any way; this
+section just shows the syntax. Third-party projects are free to use function
+annotations for documentation, type checking, and other uses.
+
+Annotations are stored in the :attr:`__annotations__` attribute of the function
+as a dictionary and have no effect on any other part of the function. Parameter
+annotations are defined by a colon after the parameter name, followed by an
+expression evaluating to the value of the annotation. Return annotations are
+defined by a literal ``->``, followed by an expression, between the parameter
+list and the colon denoting the end of the :keyword:`def` statement. The
+following example has a positional argument, a keyword argument, and the return
+value annotated with nonsense::
+
+ >>> def f(ham: 42, eggs: int = 'spam') -> "Nothing to see here":
+ ... print("Annotations:", f.__annotations__)
+ ... print("Arguments:", ham, eggs)
+ ...
+ >>> f('wonderful')
+ Annotations: {'eggs': <class 'int'>, 'return': 'Nothing to see here', 'ham': 42}
+ Arguments: wonderful spam
+
+
.. _tut-codingstyle:
Intermezzo: Coding Style
--
Repository URL: http://hg.python.org/cpython
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