Future Class Reference

Inherits object.

Collaboration diagram for Future:

Public Member Functions
def	__init__ (self)
def	setObject (self, obj)
def	clear (self)
def	isSet (self)
def	isEmpty (self)
def	getObjectWait (self, timeout=10.0)
def	__call__ (self, timeout=10.0)
def	__enter__ (self)
def	__exit__ (self, exc_type, exc_value, tb)

Static Public Member Functions
def	get (obj, timeout=10.0)

Public Attributes
	obj
	event

Detailed Description

An implementation of the Future Object design pattern. This acts as a proxy for a result from some concurrent task
which can be given to clients. When the task completes the result is given to the object, which can be retrieved
through the 'getObjectWait' function of the call () operator. If the result hasn't arrived yet then the caller will
block until it does, or when the optional timout period has elapsed. These objects work only for threads and not
between processes.

Futures can be used in a 'with' control block, such that they will send the client an exception if the block is
left without a result being sent or if an exception is thrown. This is useful in preventing client deadlock when
errors occur.

Constructor & Destructor Documentation

__init__()

def __init__

(

self

)

Member Function Documentation

__call__()

def __call__	(		self,
			timeout = 10.0
	)

Same as getObjectWait().

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__enter__()

def __enter__

(

self

)

Used to define with-blocks in which the Future must be given a value. If the block exits without a value set,
__exit__ will set the object to a FutureError indicating this. This also includes the case where the block
exits because of a raised exception, the details of which will be stored in the FutureError object.

__exit__()

def __exit__	(		self,
			exc_type,
			exc_value,
			tb
	)

Sets the stored object to a FutureError if block exits without a value or because of a raised exception.

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clear()

def clear

(

self

)

Remove the internal object and clear the event.

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get()

def get (   obj,   timeout = 10.0  )

static

Retrieve the object from `obj' if it's a Future, otherwise return `obj' itself. This is useful for methods which
may want to accept a Future containing an object or the object itself, depending on whether the use context is
concurrent or not. The `timeout' value is only used if `obj' is a Future, and must then be a positive float.

getObjectWait()

def getObjectWait	(		self,
			timeout = 10.0
	)

Return the stored object, waiting `timeout' seconds for the object to be set, returning None if this doesn't
occur in this time. If the object is present and is an exception, this is raised instead. The `timeout'
value therefore must be a positive float or None to indicate indefinite waiting. If a timeout value is given
and the return result is None, the timeout time was reached if isSet() returns False at this point, otherwise
None was the set value.

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isEmpty()

def isEmpty

(

self

)

Returns True if there is no result and the event is not set.

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isSet()

def isSet

(

self

)

Returns True if the event has been set, ie. a result is stored.

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setObject()

def setObject	(		self,
			obj
	)

Set the internal stored object to `obj' and set the event.

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Member Data Documentation

event

event

obj

obj

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The documentation for this class was generated from the following file:

• eidolon/Utils.py