Python Language Coroutines


Generators can be used to implement coroutines:

# create and advance generator to the first yield
def coroutine(func):
    def start(*args,**kwargs):
        cr = func(*args,**kwargs)
        return cr
    return start

# example coroutine
def adder(sum = 0):
    while True:
        x = yield sum
        sum += x

# example use
s = adder()
s.send(1) # 1
s.send(2) # 3

Coroutines are commonly used to implement state machines, as they are primarily useful for creating single-method procedures that require a state to function properly. They operate on an existing state and return the value obtained on completion of the operation.