This community-built FAQ covers the “Custom Iterators I” exercise from the lesson “Iterables and Iterators”.
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This exercise can be found in the following Codecademy content: Learn Intermediate Python 3
FAQs on the exercise Custom Iterators I
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The gist of this portion of the lesson is that custom classes are not iterable by default. For instance, the following code would not work.
class FishInventory:
def __init__(self, fishList):
self.available_fish = fishList
fish_inventory_cls = FishInventory(["Bubbles", "Finley", "Moby"])
for i in fish_inventory_cls:
print(i)
However, if I wanted to operate on the list passed in as fishList, what’s stopping me from doing the following?
class FishInventory:
def __init__(self, fishList):
self.available_fish = fishList
fish_inventory_cls = FishInventory(["Bubbles", "Finley", "Moby"])
for i in fish_inventory_cls.available_fish:
print(i)
This is my second time running through the lesson, and it still is not super clear as to what additional functionality adding the custom iterators will offer. I’m hoping somebody could offer some insight.
By default, custom classes are not iterable. We can’t just go around plugging our custom classes into for loops and expecting any results! This presents a problem if the class we are working with needs the ability to iterate.
When we create a FishInventory class object, we want to iterate over all the fish available within self.available_fish
Okay…so just do this:
f = FishInventory(["Bubbles", "Finley", "Moby"])
all_fishes = f.available_fish
for fish in all_fishes:
print(fish)
I guess that its possible to eliminate the error by returning an iterator object for the __iter__ method. (Iterator objects were mentioned in a previous part of the lesson.)
I added the following code to the class:
) below.
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