diff options
| -rw-r--r-- | PEP.txt | 74 | ||||
| -rw-r--r-- | python2/futures/_base.py | 4 | ||||
| -rw-r--r-- | python3/futures/_base.py | 2 |
3 files changed, 73 insertions, 7 deletions
@@ -1,12 +1,78 @@ """ Abstract + This PEP proposes a design for a module that facilitates the evaluation of + callables using threads. + +Motivation + Python currently has powerful primitives to construct multi-threaded applications but parallelizing simple functions requires a lot of - setup work i.e. explicitly launching threads, constructing a - work/results queue, and waiting for completion or some other - termination condition (e.g. exception, success). It is also hard to - manage the global . This PEP proposes the addition + work i.e. explicitly launching threads, constructing a work/results queue, + and waiting for completion or some other termination condition (e.g. + failure, timeout). It is also difficult to design an application with a + global thread limit when each component must invent its own threading + stategy. + +Specification: + + +Executor: + .run_to_futures(calls, timeout=None, return_when=ALL_COMPLETED) + + Schedule the given calls for execution and return a FutureList + containing a Future`for each call. + + *calls* must be a sequence of callables that take no arguments. + + *timeout* can be used to control the maximum number of seconds to wait before + returning. If *timeout* is not specified or None then there is no limit + to the wait time. + + *return_when* indicates when the method should return. It must be one of the + following constants: + + FIRST_COMPLETED - The method will return when any call finishes. | + FIRST_EXCEPTION - The method will return when any call raises an exception + or when all calls finish. | + ALL_COMPLETED - The method will return when all calls finish. | + +-----------------------------+----------------------------------------+ + | :const:`RETURN_IMMEDIATELY` | The method will return immediately. | + +-----------------------------+----------------------------------------+ + + + The core idea behind the module is the concept of a Future. A Future is a + XXX. The Future class makes little committement to the evaluation mode + being used e.g. the same class could be used for lazy or eager evaluation, + for evaluation using threads or using remote procedure calls. + + Future implements a single operation: + - cancel(): Cancels the Future if possible. Returns True if the + operation was cancelled, False otherwise. + + and several getters: + - cancelled: True if the Future was cancelled, False otherwise + - running: True if the call that the Future represents is currently + being evaluated, False otherwise. + - done: True if the + - result + - exception + + +Rationale: + + The proposed design of this module was heavily influenced by the the Java + XXX package [1]. The conceptual basis of the module is the Future class [2], which + is XXX. + The Future class makes little committement to the evaluation mode + being used e.g. if can be be used for lazy or eager evaluation, for evaluation + using threads or using remote procedure calls. Futures have already been + seen in Python as part of recipe [XXX]. + + Futures are created by an Excecutor [Java ref]. An Executor takes callables + as arguments and returns a list of Future instances. + + This PEP proposes the addition Python currently distinguishes between two kinds of integers diff --git a/python2/futures/_base.py b/python2/futures/_base.py index 4c50064..bec7212 100644 --- a/python2/futures/_base.py +++ b/python2/futures/_base.py @@ -545,7 +545,7 @@ class Executor(object): RETURN_IMMEDIATELY - Return without waiting. Returns: - A FuturesList containing futures for the given calls. + A FutureList containing Futures for the given calls. """ raise NotImplementedError() @@ -580,7 +580,7 @@ class Executor(object): else: yield future.result(end_time - time.time()) except Exception, e: - # Python 2.4 and earlier didn't allow yield statements in + # Python 2.4 and earlier don't allow yield statements in # try/finally blocks try: fs.cancel(timeout=0) diff --git a/python3/futures/_base.py b/python3/futures/_base.py index ad338ae..330423e 100644 --- a/python3/futures/_base.py +++ b/python3/futures/_base.py @@ -484,7 +484,7 @@ class Executor(object): RETURN_IMMEDIATELY - Return without waiting. Returns: - A FuturesList containing futures for the given calls. + A FutureList containing Futures for the given calls. """ raise NotImplementedError() |