nesting python generators (one inside another)

Question

I have two functions (generator).

def a():
  yield 1
  yield 2


def b():
  yield 'A'
  yield 'B'
  yield a()

Now I want to iterate over b() and expect it should output A B 1 2. But no. Its giving this.

In [11]: for i in b():
   ....:     print i
   ....:     
A
B
<generator object a at 0x10fc3ddc0>

How can I get the required output?

Why would you expect A B 1 2? You're yielding the generator object itself, not its contents. — jonrsharpe
– jonrsharpe, Commented Mar 11, 2015 at 16:15

mgilson · Accepted Answer · 2015-03-11 16:17:20Z

6

On python3.3+, you can use yield from:

def b():
    yield 'A'
    yield 'B'
    yield from a()

In versions prior to python3.3, you need to yield the values explicitly in a loop:

def b():
    yield 'A'
    yield 'B'
    for item in a():
        yield item

answered Mar 11, 2015 at 16:17

mgilson

312k70 gold badges656 silver badges722 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Shiplu Mokaddim Over a year ago

My bad luck its not available on python2. But this is what I expected actually!

mgilson Over a year ago

@ReutSharabani -- Sorry, it means I was having a hard time typing :-) You should still be able to see my comment on your now deleted post, but basically I was pushing back on the notion that yield from is simply "syntatic sugar" as it is true generator delegation -- and accomplishing the same thing prior to yield from is tricky.

user4659069 · Accepted Answer · 2015-03-11 16:20:22Z

1

In Python 3. You could use yield from

def a():
  yield 1
  yield 2


def b():
  yield 'A'
  yield 'B'
  yield from a()

answered Mar 11, 2015 at 16:20

user4659069

Collectives™ on Stack Overflow

nesting python generators (one inside another)

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related