From 19d0c29e7eda192da4ecb0210fb67d0c84a39415 Mon Sep 17 00:00:00 2001 From: Michele Simionato Date: Sun, 14 Jan 2018 07:34:06 +0100 Subject: Regenerated the docs --- docs/tests.documentation.rst | 82 ++++++++++++++++++++++++++++++++------------ 1 file changed, 61 insertions(+), 21 deletions(-) (limited to 'docs') diff --git a/docs/tests.documentation.rst b/docs/tests.documentation.rst index f77cb10..df04e7c 100644 --- a/docs/tests.documentation.rst +++ b/docs/tests.documentation.rst @@ -3,7 +3,7 @@ The ``decorator`` module :Author: Michele Simionato :E-mail: michele.simionato@gmail.com -:Version: 4.1.2 (2017-07-23) +:Version: 4.1.2 (2018-01-14) :Supports: Python 2.6, 2.7, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6 :Download page: http://pypi.python.org/pypi/decorator/4.1.2 :Installation: ``pip install decorator`` @@ -39,9 +39,9 @@ What's New in version 4 - **New documentation** There is now a single manual for all Python versions, so I took the - opportunity to overhaul the documentation. So, even if you are - a long-time user, you may want to revisit the docs, since several - examples have been improved. + opportunity to overhaul the documentation and to move it to readthedocs.org. + Even if you are a long-time user, you may want to revisit the docs, since + several examples have been improved. - **Packaging improvements** The code is now also available in wheel format. Integration with @@ -72,6 +72,11 @@ What's New in version 4 defined with the `async def` syntax, and to maintain the `inspect.iscoroutinefunction` check working for the decorated function. +- **Decorator factories** + + From version 4.2 there is facility to define factories of decorators in + a simple way, a feature requested by the users since a long time. + Usefulness of decorators ------------------------------------------------ @@ -465,31 +470,66 @@ Here is an example of usage: >>> func() calling func with args (), {} +The `decorator` function can also be used to define factories of decorators, +i.e. functions returning decorators. In general you can just write something +like this: + +.. code-block:: python + + def decfactory(param1, param2, ...): + def caller(f, *args, **kw): + return somefunc(f, param1, param2, .., *args, **kw) + return decorator(caller) + +This is fully general but requires an additional level of nesting. For this +reasone since version 4.2 there is a facility to build +decorator factories by using a single caller with default arguments i.e. +writing something like this: + +.. code-block:: python + + def caller(f, param1=default1, param2=default2, ..., *args, **kw): + return somefunc(f, param1, param2, *args, **kw) + decfactory = decorator(caller) + +Notice that this simplified approach *only works with default arguments*, +i.e. `param1`, `param2` etc must have known defaults. Thanks to this +restriction, there exists an unique default decorator, i.e. the member +of the family which uses the default values for all parameters. Such +decorator can be written as `decfactory()` with no parameters specified; +moreover, as a shortcut, it is also possible to elide the parenthesis, +a feature much requested by the users. For years I have been opposite +to this feature request, since having expliciti parenthesis to me is more clear +and less magic; however once this feature entered in decorators of +the Python standard library (I am referring to the dataclass decorator +https://www.python.org/dev/peps/pep-0557/) I finally gave up. + +The example below will show how it works in practice. + ``blocking`` ------------------------------------------- Sometimes one has to deal with blocking resources, such as ``stdin``. Sometimes it is better to receive a "busy" message than just blocking everything. -This can be accomplished with a suitable family of decorators, -where the parameter is the busy message: +This can be accomplished with a suitable family of decorators (decorator +factory), parameterize by a string, the busy message: .. code-block:: python - def blocking(not_avail): - def _blocking(f, *args, **kw): - if not hasattr(f, "thread"): # no thread running - def set_result(): - f.result = f(*args, **kw) - f.thread = threading.Thread(None, set_result) - f.thread.start() - return not_avail - elif f.thread.isAlive(): - return not_avail - else: # the thread is ended, return the stored result - del f.thread - return f.result - return decorator(_blocking) + @decorator + def blocking(f, msg='blocking', *args, **kw): + if not hasattr(f, "thread"): # no thread running + def set_result(): + f.result = f(*args, **kw) + f.thread = threading.Thread(None, set_result) + f.thread.start() + return msg + elif f.thread.isAlive(): + return msg + else: # the thread is ended, return the stored result + del f.thread + return f.result Functions decorated with ``blocking`` will return a busy message if @@ -498,7 +538,7 @@ available. For instance: .. code-block:: python - >>> @blocking("Please wait ...") + >>> @blocking(msg="Please wait ...") ... def read_data(): ... time.sleep(3) # simulate a blocking resource ... return "some data" -- cgit v1.2.1