FAQ: Hash Maps: Python - Creating the Hash Map Class

This community-built FAQ covers the “Creating the Hash Map Class” 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 Creating the Hash Map Class

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Can someone please explain step 3 of this exercise? I dont understand why this step must be taken:

Create an instance variable called .array , which is a list of size array_size . Make each element of .array equal to None .

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I know this reply arrived wayyyy too late but maybe it’ll help for future learners:
I think “None” here represents a default value or an “empty slot” in our array, which can be filled with data later. And we put it in range(self.array_size) because we can’t have more emty slots than the size of our array.
That’s how I understand this :slight_smile:


I don’t think these lessons make it clear enough that Python is being used as merely as a tool to illustrate how this data-structure functions. I would suggest a more clear statement at the outset, such as “in Python, efficient key-value storage via hash-maps is already accomplished via the built in dictionary Data-Type, that you will already have learned about by now. For that reason, this exercise is focusing on teaching you the general principles of how hash-maps may be implemented across different programming languages. In practice with Python, you’ll likely want to use the built-in dictionary class for most purposes.”

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self.array = [None] * array_size

This is a bit easier syntax…

Is this a correct statement about Python? It is from the lesson ‘Creating the Hash Map Class’.

“In Python we don’t have an array data structure that uses a contiguous block of memory.”

The following article says the opposite about Python arrays:

“This is because Python arrays use contiguous blocks of memory, which makes them easier to access and process.”
Source: Introduction to Python arrays

So, which one is true about Python arrays?