pypromise 0.4

Description:

pypromise 0.4

Promise
This is a implementation of Promises in Python. It is a super set of
Promises/A+ designed to have readable, performant code and to provide
just the extensions that are absolutely necessary for using promises in
Python.
Its fully compatible with the Promises/A+
spec


Installation
$ pip install pypromise


Usage
The example below shows how you can load the promise library. It then
demonstrates creating a promise from scratch. You simply call
Promise(fn). There is a complete specification for what is returned
by this method in
Promises/A+.
from promise import Promise

promise = Promise(
lambda resolve, reject: resolve('RESOLVED!')
)


API
Before all examples, you will need:
from promise import Promise

Promise(resolver)
This creates and returns a new promise. resolver must be a function.
The resolver function is passed two arguments:

resolve should be called with a single argument. If it is called
with a non-promise value then the promise is fulfilled with that
value. If it is called with a promise (A) then the returned promise
takes on the state of that new promise (A).
reject should be called with a single argument. The returned
promise will be rejected with that argument.



Static Functions
These methods are invoked by calling Promise.methodName.

Promise.resolve(value)
Converts values and foreign promises into Promises/A+ promises. If you
pass it a value then it returns a Promise for that value. If you pass it
something that is close to a promise (such as a jQuery attempt at a
promise) it returns a Promise that takes on the state of value
(rejected or fulfilled).


Promise.reject(value)
Returns a rejected promise with the given value.


Promise.all(list)
Returns a promise for a list. If it is called with a single argument
then this returns a promise for a copy of that list with any promises
replaced by their fulfilled values. e.g.
p = Promise.all([Promise.resolve('a'), 'b', Promise.resolve('c')]) \
.then(lambda res: res == ['a', 'b', 'c'])

assert p.value is True



Instance Methods
These methods are invoked on a promise instance by calling
myPromise.methodName


promise.then(on_fulfilled, on_rejected)
This method follows the Promises/A+
spec. It explains
things very clearly so I recommend you read it.
Either on_fulfilled or on_rejected will be called and they will
not be called more than once. They will be passed a single argument and
will always be called asynchronously (in the next turn of the event
loop).
If the promise is fulfilled then on_fulfilled is called. If the
promise is rejected then on_rejected is called.
The call to .then also returns a promise. If the handler that is
called returns a promise, the promise returned by .then takes on the
state of that returned promise. If the handler that is called returns a
value that is not a promise, the promise returned by .then will be
fulfilled with that value. If the handler that is called throws an
exception then the promise returned by .then is rejected with that
exception.

promise.catch(on_rejected)
Sugar for promise.then(None, on_rejected), to mirror catch in
synchronous code.


promise.done(on_fulfilled, on_rejected)
The same semantics as .then except that it does not return a promise
and any exceptions are re-thrown so that they can be logged (crashing
the application in non-browser environments)




Other package functions

is_thenable(obj)
This function checks if the obj is a Promise, or could be
promisifyed.


promisify(obj)
This function wraps the obj act as a Promise if possible. Python
Futures are supported, with a callback to promise.done when
resolved.




Notes
This package is heavily insipired in
aplus.

License
MIT
License