Yield multiple values

Question

Can't we yield more than one value in the python generator functions?

Example,

def gen():
    for i in range(5):
        yield i, i+1
            
k1, k2 = gen()

---

Traceback (most recent call last)
----> 1 k1, k2 = a()

ValueError: too many values to unpack

This works as follows:

>>> b = a()

>>> list(b)
[(0, 1), (1, 2), (2, 3), (3, 4), (4, 5)]

Same results even when I do this:

def a():
    for i in range(5):
        yield i
        yield i+1

Answer 1

Because gen() returns a generator (a single item - so it can't be unpacked as two), it needs to be advanced first to get the values...

g = gen()
a, b = next(g)

It works with list because that implicitly consumes the generator.

Can we further make this a generator? Something like this:

g = gen();
def yield_g():
    yield g.next();
    k1,k2 = yield_g();

and therefore list(k1) would give [0,1,2,3,4] and list(k2) would give [1,2,3,4,5].

Keep your existing generator, and use izip (or zip):

from itertools import izip
k1, k2 = izip(*gen())