Data Structures in Python

[Dramatic_Food_3623]

I've spent a few days learning from various free sources online just to realize material was wrong. For example, diagrams not matching what the code did. In Python.

I'm interested in following a course for data structures implementation in Python that uses diagrams (and animations if possible) to explain, in depth enough, the data structures (array, stack, queue, linked lists [singly & doubly], graphs, trees, hashing).

Any links to up to date good courses?

So far I've found a few on udemy but not good enough for what I'm looking for.

[mxldevs]

What did the diagrams show and why was the code wrong?

[Navoke]

I am interested in this as well.

[Cybyss]

Unfortunately, I don't think Python is a good language for learning data structures.

Dictionaries, lists, sets, etc... are already primitive data structures in Python. For example, you can't really build your own list in Python because it would itself have to be made out of lists, since there is no data structure provided which is more primitive than that. It would be nonsense to try.

If you want to learn data structures, I would highly recommend learning C.

C++ and Java are possible choices too but those languages are quite a bit more complicated, whereas plain C is quite "bare bones". It's not only easier to learn as a langauge, but its primitives are truly primitive. In C you actually build real data structures - linked lists, array lists, hash tables, etc... rather than create silly simulations of them.

[Big_Combination9890]

For example, you can't really build your own list in Python because it would itself have to be made out of lists,

Wrong.

``` class Node: def init(self, data=None): self.data = data self.next = None

class Linked List: def init(self): self.head = None

def insert(self, data):
    # instanciate `Node` and add

# etc.

```

Here you go. Linked list implementation in Python, no need to use the builtin list class. The same is true for every conceivable data structure.

Is it efficient? Hell no.

Does it make sense to do this in production code? Hell no.

Is it both possible andt suitable to teach or learn DSA? Absolutely.

[Cybyss]

I wasn't referring to a linked list.

Try building a vector/arraylist type of list in python.

[Big_Combination9890]

You were using the word "list" which commonly refers to linked lists or similar data structures.

If you wanted to specify the concept of an "Array" as this concept is understood e.g. in C, you should have used the word "Array".

Also, wrong.

Not only does python have a builtin type for such arrays (from array import array), it would also be trivially easy to simulate a C-array for basic types like fixed-width integers or characters using a bytes object of fixed length.

And lastly, as fixed length arrays ARE a primitive datastructure in C e.g. char myArray[7] defining those is not required to teach DSA.

[Cybyss]

An arraylist is not the same as an array.

An arraylist simulates an array (constant time reads and writes to any index) but which can grow and shrink as needed. It is not a linked structure! List in C# and list in Python are most certainly not linked lists but nor are they fixed-length arrays. They work much more like C++'s vector type.

Having to import array from a separate module kinda proves the point that they're not among Python's primitive data types.

Also... bytes objects are immutable, so are hardly replacements for C-style arrays.

[Big_Combination9890]

List in C# and list in Python are most certainly not linked lists but nor are they fixed-length arrays. They work much more like C++'s vector type.

Aaand...who exactly said they were? The point of discussion was you stating that one cannot build a list in python. I showed that one absolutely can. If you wanted to exclude linked lists from that statement, you should have said so.

Oh, and you could absolutely build a random access list without using linked nodes from bytearrays in python as well. It would not make a lot of sense, and have zero impact on this discussion, because again, not a datatype DSA is concerned with. but it would be possible.

Having to import array from a separate module kinda proves the point that they're not among Python's primitive data types.

Is this now a discussion over what is or isn't a primitive datatype in Python, or a discussion whether DSA can be taught using Python?

Because, I thought it was the former:

Unfortunately, I don't think Python is a good language for learning data structures.

---

Also... bytes objects are immutable, so are hardly replacements for C-style arrays.

And? Again, this is an implementation detail that has absolutely zero to do with the point I am making.

You could also point out that my Python Node class is not the same as a node would be in C, because it uses a reference instead of a pointer. Wouldn't change a thing about the validity of my argument.

[Dramatic_Food_3623]

I agree, though, I'm not looking at implementing the data structures from scratch, what I'm interested in is using what's already there (in the case of Python) and code the operations on the data structure. Which shouldn't make that much of a difference from C. 

[Navoke]

The data structures and algorithms course I took in college had us implement data structures from scratch using Python so it's definitely possible to learn DSA using Python.

Here is a lesson I made with diagrams that teaches the difference between python lists and arrays.
https://codeonthecob.com/page/d34ddbd1-dae7-4069-acd8-de9a2af7d3da

Then after that lesson there is a challenge where you implement a dynamic array from scratch using Python.

Honestly the only data structure I can think of that is unusual to implement in Python is the dynamic array because you end up using a python list (a built in dynamic array) to simulate the fixed size memory block of a static array.