Making the Linked List Iterable

Working With Linked Lists in Python Austin Cepalia 01:50

Transcript
Discussion (2)

00:00 Earlier, I mentioned that one limitation of our LinkedList is that there’s no easy way to use it as an iterable—that is, we can’t use it in places where an iterable type is expected, such as in a for loop. To mitigate this, we added a .__repr__() method that returned a formatted string representation of the LinkedList—but that’s really more useful in the context of debugging than anywhere else. To make our LinkedList iterable so we can step through each Node one by one, all we need to do is add a .__iter__() method.

00:38 Just like before, we start by creating a new variable for the current node and setting it equal to the .head of the LinkedList.

00:47 Now we can say while node is not None, yield the current node and set the current node to the next one. This special yield keyword is similar to return, except that it doesn’t stop execution of the current method once it’s reached.

01:06 And that’s all it takes to make our LinkedList iterable. Let’s try it out in the interactive shell.

01:14 for node in llist: print(node). Remember, printing the Node will print its .data value. And, there is all the data.

01:29 In other articles, you might see traversal code like this wrapped inside a method called traverse() or something similar. We can absolutely do that here, but it’s a bit more Pythonic if we take advantage of the .__iter__() method provided by the language to make our list an iterable type.

Aashay on June 1, 2025

How does print(node) prints the node’s data value?

All we have is a .__repr__() method defined which prints all the nodes, as mentioned useful for debugging!

Bartosz Zaczyński RP Team on June 3, 2025

@Aashay The print() function calls str() on the object passed as an argument in order to convert it into a string representation. Under the hood, str() calls the object’s .__str__() method, and when that method can’t be found, Python falls back to calling .__repr__(), as shown here:

>>> class Person:
...     def __init__(self, name):
...         self.name = name
...     
...     def __repr__(self):
...         return f"Person(name={self.name!r})"
...

>>> person = Person("John")

>>> print(person)
Person(name='John')

>>> str(person)
"Person(name='John')"

>>> repr(person)
"Person(name='John')"

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