Help me understand why yield total doesn't comes out as 0 at the first calling!
Since [sumer] passed though [primer] by @coroutine, [su] already met next() in side of primer right?
So I'm guessing the result of print('EX2-1 -',su)
should be
0
But the real result turns out to be just showing the address of su,
and only after su.send(100) the value comes out as 100
What am I missing??
from functools import wraps
from inspect import getgeneratorstate
def coroutine(func):
@wraps(func)
def primer(*args, **kwargs):
gen = func()
next(gen)
return gen
return primer
@coroutine
def sumer():
total = 0
term = 0
while True :
term = yield total
print('term recieved')
total += term
su = sumer()
print('EX2-1 -',su)
print(getgeneratorstate(su))
print('EX2-1 -', su.send(100))
Let's go through your code step by step.
The coroutine decorator is gonna return it's inner function which is primer and that's it... So after you apply @coroutine to the sumer , the sumer label is now pointing to the primer function.
Next when you call the primer function in line su = sumer(), it will create a coroutine in line gen = func() then primes it with next(gen) and returns the primed coroutine.
Up until now su is pointing to whatever the primer function returned, which is a generator not the value !
Your problem is exactly here, if the primer returns next(gen) you will get 0. But that 0 is just skipped and your coroutine is now ready to receive values.
Try to change it to:
from functools import wraps
def coroutine(func):
@wraps(func)
def primer(*args, **kwargs):
gen = func()
return next(gen)
return primer
@coroutine
def sumer():
total = 0
while True:
term = yield total
print('term recieved')
total += term
su = sumer()
print('EX2-1 -', su)
It is 0 now but not useful anymore.
Since su is not the generator anymore, you can't pass it to the getgeneratorstate and also send value to it. It is an integer now.