Chaining coroutines for number crunching workflows...

co_workflow.py

TARGETS = 'targets'
    
class AnalysisWindowComplete(Exception):
    """
    Used in coroutine control flow, this is not an error condition.
    """
    

def coroutine(func):
    """
    Decorator function for coroutines to automatically call next so that they are in 
    a ready state when they are called. (from dabeaz)
    """    
    
    def start(*args, **kwargs):
        g = func(*args, **kwargs)
        g.next()
        return g
    return start

@coroutine
def myprinter(name):
    while True:      
        p = (yield) 
        print "printer %s says: %s" % (name, p)
        
@coroutine
def average(targets):

    result = 0.0
    
    
    try:
        while True:
            cnt = 0
            try:
                
                while True:      
                    val = (yield) 
                    result += val
                    cnt += 1
        
            except AnalysisWindowComplete as wc:
            
                print 'In finalize with:', wc
                result = result/cnt
                
                for target in targets:
                    target.send(result)
            
                result = 0.0
            
    except (ValueError, IndexError) as e:
        raise

            
def get_targets(co):

    try:
        return co.gi_frame.f_locals[TARGETS]
    except KeyError as ke:
        print 'foo bar muck up...'
        
                
def set_targets(co, targets):
    
    t = get_targets(co)
    
    while len(t) > 0:
        t.pop()
    
    for target in targets:
        t.append(target)
         
            

avg_co = average([myprinter('Initial...'),] )

avg_co.send(5.)
avg_co.send(5.)
avg_co.send(5.)
avg_co.send(4.)

avg_co.throw(AnalysisWindowComplete,'foo')

# Now continue using the same coroutine workflow for next analysis
avg_co.send(6)
avg_co.send(6)
avg_co.send(7)

# change where things go...
set_targets(avg_co,(myprinter('barbaz'),myprinter('boo')) )

avg_co.throw(AnalysisWindowComplete,'goo')
# but if you want to chain these - you spend a lot of time calling throw and creating exceptions!
# maybe try a class decorator to memoize __init__ for the exception?
# maybe try an allocation pool?
# or just make sure your program spends way more time in the main part of the workflow that uses send...
# If you are using this to throw all the time your doing it wrong.