Today I learned that Python generators can return a value.

Generators

Generators are interesting Python objects that produce a series of values, but one by one. In a way, they can be thought of as stateful functions. (That is, functions with state.)

What I learned is that generators can also return something. Here is the tweet that prompted this discovery:

#Python pop quiz: Is this code valid? If so, what does it do?

def f():
yield 10
return 20

g = f()
print(next(g))
print(next(g))

— Raymond Hettinger (@raymondh) October 7, 2021

Returning from a generator

When you use a return inside a generator, the generator will have that returned information in its StopIteration exception when it's done:

>>> def f():
...     yield 10
...     return 20
...
>>> gen = f()
>>> next(gen)
10
>>> next(gen)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration: 20

If you want to get access to that value, you just need to catch the exception:

>>> gen = f(); next(gen);
10
>>> try:
...     next(gen)
... except StopIteration as e:
...     val = e.value
...
>>> val
20

That's it for now! Stay tuned and I'll see you around!

Espero que tenhas aprendido algo novo! Se sim, considera seguir as pisadas dos leitores que me pagaram uma fatia de pizza 🍕. O teu pequeno contributo ajuda-me a manter este projeto grátis e livre de anúncios aborrecidos.