def example_BackgroundCall():
import urllib,time
def work():
return urllib.urlopen('http://www.python.org/').read()
bkcall=BackgroundCall(work)
print 'work() executing in background ...'
while not bkcall.is_done():
print '.',
time.sleep(0.010)
print 'done.'
print bkcall.get_return()[:500]
import sys
from time import time as _time, sleep as _sleep
class Full(Exception):pass
class Empty(Exception):pass
class BackgroundCall:
"""BackgroundCall
Example:
bkcall=BackgroundCall( time_consuming_function )
...
if bkcall.is_done():
print "got", bkcall.get_return()
"""
id=None
done=0 #1=returned; 2=exception raised
def __init__(self, func, args=(), kwargs={}):
import thread
def thread_bkcall():
try:
self.ret=func(*args, **kwargs)
self.done=1
except:
self.exc=sys.exc_info()
self.done=2
self.id=thread.start_new(thread_bkcall, ())
def is_done(self):
return self.done
def get_return(self, wait=1, timeout=None, raise_exception=1, alt_return=None):
"""delivers the return value or (by default) echoes the exception of
the call job
wait: 0=no waiting; Attribute error raised if no
1=waits for return value or exception
callable -> waits and wait()-call's while waiting for return
"""
if not self.done and wait:
starttime=_time()
delay=0.0005
while not self.done:
if timeout:
remaining = starttime + timeout - _time()
if remaining <= 0: #time is over
if raise_exception:
raise Empty, "return timed out"
else:
return alt_return
delay = min(delay * 2, remaining, .05)
else:
delay = min(delay * 2, .05)
if callable(wait): wait()
_sleep(delay) #reduce CPU usage by using a sleep
if self.done==2: #we had an exception
exc=self.exc
del self.exc
if raise_exception & 1: #by default exception is raised
raise exc[0],exc[1],exc[2]
else:
return alt_return
return self.ret
def get_exception(self):
return self.exc
if __name__=='__main__':
example_BackgroundCall()
