CODEWITHSUNDEEP
pythonpython-2.7
oschlueter
oschlueter

Reputation: 2698

Calling coroutine from coroutine in python

I came across this issue today and I'm not quite certain why it works like this:

def outside():
    print 'before'
    inside()
    print 'after'
    yield 'World'

def inside():
    print 'inside'
    yield 'Hello'

for n in outside():
    print n

(Naive) expectation of output:

before
inside
Hello
after
World

Actual output:

before
after
World

Is it not possible to call a coroutine from inside a coroutine? The articles I read on coroutines and yield didn't elaborate on this issue and I'm quite lost here. Could anyone shed some light on this behaviour please? Thanks in advance!

Upvotes: 3

Views: 1101

Answers (1)

mitghi
mitghi

Reputation: 919

It is totally possible. when you call inside() it creates a coroutine. In order to yield the result, you need to initialize the coroutine and yield from it as follows:

def outside():
     print 'before'
     for i in inside():
         yield i
     print 'after'
     yield 'World'

and the result would be as expected:

before
inside
Hello
after
World

Upvotes: 3

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