Adisp is a library that allows structuring code with asynchronous calls and callbacks without defining callbacks as separate functions.
The code then becomes sequential and easy to read. The library is not a framework by itself and can be used in other environments that provides asynchronous working model (see an example with Tornado server in examples/proxy_example.py).
To install adisp you can use easy_install:
easy_install adisp
or via pip:
pip adisp
All the magic is done with Python 2.5 decorators that allow for control flow to leave a function, do sometihing else for some time and then return into the calling function with a result. So the function that makes asynchronous calls should look like this:
@process
def my_handler():
response = yield some_async_func()
data = parse_response(response)
result = yield some_other_async_func(data)
store_result(result)
Each yield is where the function returns and lets the framework around it to
do its job. And the code after yield is what usually goes in a callback.
The @process decorator is needed around such a function. It makes it callable
as an ordinary function and takes care of dispatching callback calls back into
it.
In the example above functions some_async_func and some_other_async_func
are those that actually run an asynchronous process. They should follow two
conditions:
- accept a
callbackparameter with a callback function that they should call after an asynchronous process is finished - a callback should be called with one parameter -- the result
- be wrapped in the
@asyncdecorator
The @async decorator makes a function call lazy allowing the @process that calls it to provide a callback to call.
Using async with @-syntax is most convenient when you write your own asynchronous function (and can make your callback parameter to be named "callback"). But when you want to call some library function you can wrap it in async in place.:
# call http.fetch(url, callback=callback) result = yield async(http.fetch) # call http.fetch(url, cb=safewrap(callback)) result = yield async(http.fetch, cbname='cb', cbwrapper=safewrap)(url)
Here you can use two optional parameters for async:
- cbname: a name of a parameter in which the function expects callbacks
- cbwrapper: a wrapper for the callback iself that will be applied before calling it
@async function can also be @process'es allowing to effectively chain
asynchronous calls as it can be done with normal functions. In this case the
@async decorator shuold be the outer one:
@async
@process
def async_calling_other_asyncs(arg, callback):
# ....
The library also allows to call multiple asynchronous functions in parallel and get all their result for processing at once:
@async
def async_http_get(url, callback):
# get url asynchronously
# call callback(response) at the end
@process
def get_stat():
urls = ['http://.../', 'http://.../', ... ]
responses = yield map(async_http_get, urls)
After all the asynchronous calls will complete responses will be a list of
responses corresponding to given urls.
Fork https://github.com/Lispython/adisp/ , create commit and pull request.
Originally adisp developed by Ivan Sagalaev, but no longer supported them.