coroutine.py

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#!/usr/bin/env python
from __future__ import division

from functools import wraps
from UserDict import IterableUserDict

def coroutine(func):
  @wraps(func)
  class wrapper(IterableUserDict):
    def __init__(self,*args,**kwargs):
      self.target = None
      self.func = func
      self.data = dict()
      self.cr = self.func(self,*args,**kwargs)
      self.initialized = False

    def __or__(self, other):
      o = self._getLast()
      o.target = other
      self.ref(other)
      return self

    def ref(self,other):
      a = other
      while a is not None:
        a.data = self.data
        a = a.target

    def _getLast(self):
      o = self
      while o.target!=None:
        o = o.target
      return o

    # send to next target
    def __call__(self,*args,**kwargs):
      if self.target!=None:
        self.target.send(*args,**kwargs)

    def send(self,*args,**kwargs):
      if not self.initialized:
        self.cr.next()
        self.initialized = True
      if len(args)==0:
        self.cr.send(None)
      else:
        self.cr.send(*args)

    def close(self):
      self.cr.close()

  return wrapper


# Example use
if __name__ == '__main__':

  @coroutine
  def printer(send):
    while True:
      s = (yield)
      print s
      send(s)

  @coroutine
  def plus(send,a):
    while True:
      v = (yield)
      send(v+a)

  @coroutine
  def plusconst(send,n):
    while True:
      d = (yield)
      c = send['const']
      send(d+c)


  p = plus(3) |  plus(2) | printer()
  p.send(1)

  p = plus(3) | printer() | plusconst('const') | printer()
  p['const'] = 5

  p.send(2)