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docs/source/interactive/autoawait.rst

@@ -1,213 +1,222 b''
 .. _autoawait:
 
 Asynchronous in REPL: Autoawait
 ===============================
 
 .. note::
 
    This feature is experimental and behavior can change betwen python and
    IPython version without prior deprecation.
 
 Starting with IPython 7.0, and when user Python 3.6 and above, IPython offer the
 ability to run asynchronous code from the REPL. Constructs which are
 :exc:`SyntaxError` s in the Python REPL can be used seamlessly in IPython.
 
 The example given here are for terminal IPython, running async code in a
 notebook interface or any other frontend using the Jupyter protocol will need to
 use a newer version of IPykernel. The details of how async code runs in
 IPykernel will differ between IPython, IPykernel and their versions.
 
 When a supported library is used, IPython will automatically allow Futures and
 Coroutines in the REPL to be ``await`` ed. This will happen if an :ref:`await
 <await>` (or any other async constructs like async-with, async-for) is use at
 top level scope, or if any structure valid only in `async def
 <https://docs.python.org/3/reference/compound_stmts.html#async-def>`_ function
 context are present. For example, the following being a syntax error in the
 Python REPL::
 
     Python 3.6.0 
     [GCC 4.2.1]
     Type "help", "copyright", "credits" or "license" for more information.
     >>> import aiohttp
     >>> result = aiohttp.get('https://api.github.com')
     >>> response = await result
       File "<stdin>", line 1
         response = await result
                               ^
     SyntaxError: invalid syntax
 
 Should behave as expected in the IPython REPL::
 
     Python 3.6.0
     Type 'copyright', 'credits' or 'license' for more information
     IPython 7.0.0 -- An enhanced Interactive Python. Type '?' for help.
 
     In [1]: import aiohttp
        ...: result = aiohttp.get('https://api.github.com')
 
     In [2]: response = await result
     <pause for a few 100s ms>
 
     In [3]: await response.json()
     Out[3]:
     {'authorizations_url': 'https://api.github.com/authorizations',
      'code_search_url': 'https://api.github.com/search/code?q={query}...',
     ...
     }
 
 
 You can use the ``c.InteractiveShell.autoawait`` configuration option and set it
 to :any:`False` to deactivate automatic wrapping of asynchronous code. You can also
 use the :magic:`%autoawait` magic to toggle the behavior at runtime::
 
     In [1]: %autoawait False
 
     In [2]: %autoawait
     IPython autoawait is `Off`, and set to use `asyncio`
 
 
 
 By default IPython will assume integration with Python's provided
 :mod:`asyncio`, but integration with other libraries is provided. In particular
 we provide experimental integration with the ``curio`` and ``trio`` library.
 
 You can switch current integration by using the
 ``c.InteractiveShell.loop_runner`` option or the ``autoawait <name
 integration>`` magic.
 
 For example::
 
     In [1]: %autoawait trio
 
     In [2]: import trio
 
     In [3]: async def child(i):
        ...:     print("   child %s goes to sleep"%i)
        ...:     await trio.sleep(2)
        ...:     print("   child %s wakes up"%i)
 
     In [4]: print('parent start')
        ...: async with trio.open_nursery() as n:
        ...:     for i in range(5):
        ...:         n.spawn(child, i)
        ...: print('parent end')
     parent start
        child 2 goes to sleep
        child 0 goes to sleep
        child 3 goes to sleep
        child 1 goes to sleep
        child 4 goes to sleep
        <about 2 seconds pause>
        child 2 wakes up
        child 1 wakes up
        child 0 wakes up
        child 3 wakes up
        child 4 wakes up
     parent end
 
 
 In the above example, ``async with`` at top level scope is a syntax error in
 Python.
 
 Using this mode can have unexpected consequences if used in interaction with
 other features of IPython and various registered extensions. In particular if you
 are a direct or indirect user of the AST transformers, these may not apply to
 your code.
 
 When using command line IPython, the default loop (or runner) does not process
 in the background, so top level asynchronous code must finish for the REPL to
 allow you to enter more code. As with usual Python semantic, the awaitables are
 started only when awaited for the first time. That is to say, in first example,
 no network request is done between ``In[1]`` and ``In[2]``.
 
 
 Effects on IPython.embed()
 ==========================
 
 IPython core being asynchronous, the use of ``IPython.embed()`` will now require
 a loop to run. By default IPython will use a fake coroutine runner which should
 allow ``IPython.embed()`` to be nested. Though this will prevent usage of the
 ``autoawait`` feature when using IPython embed. 
 
 You can set explicitly a coroutine runner for ``embed()`` if you desire to run
 asynchronous code, the exact behavior is though undefined.
 
+Effects on Magics
+=================
+
+A couple of magics (``%%timeit``, ``%timeit``, ``%%time``, ``%%prun``) have not
+yet been updated to work with asynchronous code and will raise syntax errors
+when trying to use top-level ``await``. We welcome any contribution to help fix
+those, and extra cases we haven't caught yet. We hope for better support in Cor
+Python for top-level Async code.
+
 Internals
 =========
 
 As running asynchronous code is not supported in interactive REPL (as of Python
 3.7) we have to rely to a number of complex workaround and heuristic to allow
 this to happen. It is interesting to understand how this works in order to
 comprehend potential bugs, or provide a custom runner.
 
 Among the many approaches that are at our disposition, we find only one that
 suited out need. Under the hood we use the code object from a async-def function
 and run it in global namespace after modifying it to not create a new
 ``locals()`` scope::
 
     async def inner_async():
         locals().update(**global_namespace)
         #
         # here is user code
         #
         return last_user_statement
     codeobj = modify(inner_async.__code__)
     coroutine = eval(codeobj, user_ns)
     display(loop_runner(coroutine))
 
 
 
 The first thing you'll notice is that unlike classical ``exec``, there is only
 one namespace. Second, user code runs in a function scope, and not a module
 scope.
 
 On top of the above there are significant modification to the AST of
 ``function``, and ``loop_runner`` can be arbitrary complex. So there is a
 significant overhead to this kind of code.
 
 By default the generated coroutine function will be consumed by Asyncio's
 ``loop_runner = asyncio.get_evenloop().run_until_complete()`` method if
 ``async`` mode is deemed necessary, otherwise the coroutine will just be
 exhausted in a simple runner. It is though possible to change the default
 runner.
 
 A loop runner is a *synchronous*  function responsible from running a coroutine
 object.
 
 The runner is responsible from ensuring that ``coroutine`` run to completion,
 and should return the result of executing the coroutine. Let's write a
 runner for ``trio`` that print a message when used as an exercise, ``trio`` is
 special as it usually prefer to run a function object and make a coroutine by
 itself, we can get around this limitation by wrapping it in an async-def without
 parameters and passing this value to ``trio``::
 
 
     In [1]: import trio
        ...: from types import CoroutineType
        ...:
        ...: def trio_runner(coro:CoroutineType):
        ...:     print('running asynchronous code')
        ...:     async def corowrap(coro):
        ...:         return await coro
        ...:     return trio.run(corowrap, coro)
 
 We can set it up by passing it to ``%autoawait``::
 
     In [2]: %autoawait trio_runner
 
     In [3]: async def async_hello(name):
        ...:     await trio.sleep(1)
        ...:     print(f'Hello {name} world !')
        ...:     await trio.sleep(1)
 
     In [4]: await async_hello('async')
     running asynchronous code
     Hello async world !
 
 
 Asynchronous programming in python (and in particular in the REPL) is still a
 relatively young subject. We expect some code to not behave as you expect, so
 feel free to contribute improvements to this codebase and give us feedback.
 
 We invite you to thoroughly test this feature and report any unexpected behavior
 as well as propose any improvement.

docs/source/whatsnew/pr/await-repl.rst

@@ -1,93 +1,99 b''
 Autowait: Asynchronous REPL
 ---------------------------
 
 Staring with IPython 7.0 and on Python 3.6+, IPython can automatically await
 code at top level, you should not need to access an event loop or runner
 yourself. To know more read the :ref:`autoawait` section of our docs, see
 :ghpull:`11265` or try the following code::
 
     Python 3.6.0
     Type 'copyright', 'credits' or 'license' for more information
     IPython 7.0.0 -- An enhanced Interactive Python. Type '?' for help.
 
     In [1]: import aiohttp
        ...: result = aiohttp.get('https://api.github.com')
 
     In [2]: response = await result
     <pause for a few 100s ms>
 
     In [3]: await response.json()
     Out[3]:
     {'authorizations_url': 'https://api.github.com/authorizations',
      'code_search_url': 'https://api.github.com/search/code?q={query}{&page,per_page,sort,order}',
     ...
     }
 
 .. note::
 
    Async integration is experimental code, behavior may change or be removed
    between Python and IPython versions without warnings.
 
 Integration is by default with `asyncio`, but other libraries can be configured, 
 like ``curio`` or ``trio``, to improve concurrency in the REPL::
 
     In [1]: %autoawait trio
 
     In [2]: import trio
 
     In [3]: async def child(i):
        ...:     print("   child %s goes to sleep"%i)
        ...:     await trio.sleep(2)
        ...:     print("   child %s wakes up"%i)
 
     In [4]: print('parent start')
        ...: async with trio.open_nursery() as n:
        ...:     for i in range(3):
        ...:         n.spawn(child, i)
        ...: print('parent end')
     parent start
        child 2 goes to sleep
        child 0 goes to sleep
        child 1 goes to sleep
        <about 2 seconds pause>
        child 2 wakes up
        child 1 wakes up
        child 0 wakes up
     parent end
 
 See :ref:`autoawait` for more information.
 
 
 Asynchronous code in a Notebook interface or any other frontend using the
 Jupyter Protocol will need further updates of the IPykernel package.
 
 Non-Asynchronous code 
 ---------------------
 
 As the internal API of IPython are now asynchronous, IPython need to run under
 an even loop. In order to allow many workflow, (like using the ``%run`` magic,
 or copy_pasting code that explicitly starts/stop event loop), when top-level code
 is detected as not being asynchronous, IPython code is advanced via a
 pseudo-synchronous runner, and will not may not advance pending tasks.
 
 Change to Nested Embed
 ----------------------
 
 The introduction of the ability to run async code had some effect on the
 ``IPython.embed()`` API. By default embed will not allow you to run asynchronous
 code unless a event loop is specified.
 
+Effects on Magics
+-----------------
+
+Some magics will not work with Async, and will need updates. Contribution
+welcome.
+
 Expected Future changes
 -----------------------
 
 We expect more internal but public IPython function to become ``async``, and
 will likely end up having a persisting event loop while IPython is running.
 
 Thanks
 ------
 
 This took more than a year in the making, and the code was rebased a number of
 time leading to commit authorship that may have been lost in the final
 Pull-Request. Huge thanks to many people for contribution, discussion, code,
 documentation, use-case: dalejung, danielballan, ellisonbg, fperez, gnestor,
 minrk, njsmith, pganssle, tacaswell, takluyver , vidartf ... And many other.