FAQ: Hash Maps: Python - Handling Collisions in the Setter


This community-built FAQ covers the “Handling Collisions in the Setter” exercise from the lesson “Hash Maps: Python”.

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This exercise can be found in the following Codecademy content:

Computer Science

Complex Data Structures

FAQs on the exercise Handling Collisions in the Setter

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Minor point, but we’re asked to check if the key stored at an index is the same as the key argument passed to assign() before being instructed to save both key & value as a list, rather than just the value. I.e. at that point in the development of this class, there is no stored key.


I spent a lot of time at that step, trying to figure out if I was missing something. Thanks for letting me known I was not the only one hehe


You are right. We cannot address step.2 before step.3 since we don’t store [key, value] in step.2.


I would say this is a major, not minor, point. I was stuck for a while trying to determine how to check for a key if there was no key saved.


Why having different keys or none should write like this?

 if current_array_value is None:
  self.array[array_index] = [key, value]

if current_array_value[0] == key:
  self.array[array_index] = [key, value]

instead of value only, it saves key as well, but in the arrar_index should be only values. Why should we do that?


The value is stored along with its key as a [key, value] pair so that the key is available to be compared against an incoming key to see if there is a collision.

The code you show inserts a given [key, value] pair in the index location if the location is empty, or over-writes the existing [key, value] pair if the key is the same as the incoming key.

If neither condition is true, i.e., if there is a collision between the existing key and the incoming, new key, a new array_index is calculated and used.

1 Like

So, this is also the reason why the key in the array is in [0], and the value will be in the [1]?