Retrieving nested dictionaries in class instances

Question

I have several classes which have dictionaries as attributes. These dictionaries store instances of other classes. The lower/nested classes also have dictionaries as attributes as well.

Currently I am writing full loops, with breaks, to retrieve the nested values. Problem is that I need to do several processes/filters on the nested dictionaries so it seems computationally expensive as well as it leading to ugly, spaghetti-like code. What I would like to do is be able to access the nested items, update the items (in-place), and continue on.. Is there a way to do this?

Example code (let's assume you might wear several socks in each shoe and have several colored toes):

class Shoe: def __init__(self): self.socks = {} # this contains instances of socks class Sock: def __init__(self): self.toes = {} # this contains instances of toes self.color = 'green' class Toe: def __init__(self): self.color = 'blue'

Now I want to look inside the Shoe instance and retrieve/update all Sock instances which are green and have blue Toes. Then update the Sock/Toe instances I retrieved so that when I access the shoe later the values have changed.

All help is appreciated!

Would a database structure work for you? Because this is one of the main reasons databases exist. — Thymen
– Thymen, Commented Jan 22, 2021 at 18:24
I don't think so - but I could very likely be wrong. This is for processing Computer Vision/Deep Learning tasks. Once the task is processed then I convert all this to JSON and send it over to the database. Isn't there latency for making db calls? (can't have latency). — Nothing here
– Nothing here, Commented Jan 22, 2021 at 18:26
I guess I should say, the latency of calling the db, and reconstructing the objects, needs to be less than the current nested loops to make it worthwhile. — Nothing here
– Nothing here, Commented Jan 22, 2021 at 18:30
How many attributes such as color do you have? If it is a single one, you might want to build a dictionary of color: instances. But if there are many this solution might be too slow. About the db, if your data is relatively small (say a few thousand entries), maintaining an in memory database would not induce (much) latency. (see docs for an example) — Thymen
– Thymen, Commented Jan 22, 2021 at 18:34

George Poliovei · Accepted Answer · 2021-01-22 18:33:16Z

I suggest that you can use a list instead of obj

class Shoe: def __init__(self): self.socks = [] # this contains instances of socks class Sock: def __init__(self): self.toes = [] # this contains instances of toes self.color = 'green' class Toe: def __init__(self): self.color = 'blue' toe = Toe() socks = Sock() socks.toes.append(toe) shoes = Shoe() shoes.socks.append(socks)

then you can iterate as you want

for s in shoes.socks: # s becomes in a list of sock for t in s.toes: # t becomes in a list of toes for color in t: print(color)

or maybe i do not understand what you really need.

greeting

Dang. Right after I posted this question I thought of using lists then I left the post up in hopes that that was not the answer. I think you are right. I am going to leave it open for about an hour to see if anyone else has a solution I am not thinking of. Then mark yours as the answer.
@DavidAlford how is this different than what you'd do with the dicts?

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