Consider the following pseudo code:
def g_user():
while True:
yield read_user_input()
def g_socket():
while True:
yield read_socket_input()
def g_combined(gu, gs):
# should read user or socket input, whichever is available
while True:
sel = select(gu, gs)
if sel.contains(gu):
yield gu.next()
if sel.contains(gs):
yield gs.next()
gc = g_combined ( g_user(), g_socket() )
How to implement this in easiest way?
Look's like someone already implemented this: http://www.dabeaz.com/generators/genmulti.py
Mirrored here:
import Queue, threading
def gen_multiplex(genlist):
item_q = Queue.Queue()
def run_one(source):
for item in source: item_q.put(item)
def run_all():
thrlist = []
for source in genlist:
t = threading.Thread(target=run_one,args=(source,))
t.start()
thrlist.append(t)
for t in thrlist: t.join()
item_q.put(StopIteration)
threading.Thread(target=run_all).start()
while True:
item = item_q.get()
if item is StopIteration: return
yield item
In order to make select.select() work properly, you'll need to expose a fileno() method on your generators that returns the underlying file descriptor.
itertools module from standard library contains nice functions. In this specific case cycle function is good.
cycle help says:
cycle(iterable) --> cycle object
Return elements from the iterable until it is exhausted. Then repeat the sequence indefinitely.
Using cycle in your solution:
import itertools
def g_user():
while True:
yield read_user_input()
def g_socket():
while True:
yield read_socket_input()
def g_combine(*generators):
for generator in itertools.cycle(generators):
yield generator.next()
g_combined = g_combine(g_user(), g_socket())
Considerations about this code:
g_combine ends with first generator that raise StopIteration
g_combine accepts N generators
How catch exceptions correctly? Think about.
__next__(), you'll need some kind ofis_ready()method.itertools.multiplex)