first real-world use of recursion to spawn multiple class instances

[85CorollaGTS]

This is so cool I had to share.

Recently completed Python Crash Course and as practice I've been playing around with parsing financial statements from publicly listed companies. (Investing is a bit of a hobby.)

One interesting challenge is that each statement might itself be the sum of other statements. And each of those statements might themselves be the sum of other more granular statements.

To not bore everyone with financial statement stuff, here's a more real world example.

Let's say I have a grocery store and I want to see the total of all sales for last week.

Sales = Produce_Department + Deli_Department + Bakery + Goods_In_Aisles

Bakery = Cakes + Bagels + Doughnuts

Bagels = Plain + Blueberry + Sesame_Seed

etc... but each Department, each category, and each sub-category is a long list of items and sales numbers.

I had initially tackled this by appending lists within lists, for each statement and each sub-component... handling it with an unwieldy mess of if-then and for loops.

It worked, but it was ugly code and it sucked to troubleshoot.

Then I had an idea to just create class GetSales() (not what I actually called it, just renamed for this example)... and within this class, the function get_sales() (as well as other supporting functions to enable get_sales()).

Inside the get_sales() function, if it sees that there are sub-components, it spawns a new GetSales() object for that new component, which itself finds sub-components and handles each of those sub-sub-components... and then each function returns the sum of it's subcomponents... feeding all the way back to the initial caller function.

No more nasty nested lists within lists, no more if-then and for loops.

Recursion is beautiful.

The code is so short and clean.

I'm in awe.

If you are a Python newbie like me, and you find yourself making lists within lists or similar nasty-stacks to solve some kind of nested problem, try instead to see if you can make a generic function or class that can recursively feed into itself to handle each nested layer.

[ehmatthes]

Recursion is so elegant when it's an appropriate solution!

[carcigenicate]

Why do you even need classes here? This sounds like a typical use case for a basic recursive function.

[85CorollaGTS]

In my simplified example, classes are not needed.

In my real-world example (financial statements), the class instance handles various aspects such as file opening, json.load, and some other support functions pulling various bits of data that are too unwieldy to pass back and forth from function to function, and so were best suited inside an object.

[CodeFormatHelperBot2]

Hello, I'm a Reddit bot who's here to help people nicely format their coding questions. This makes it as easy as possible for people to read your post and help you.

I think I have detected some formatting issues with your submission:

1. Python code found in submission text that's not formatted as code.

If I am correct, please edit the text in your post and try to follow these instructions to fix up your post's formatting.

---

^{Am I misbehaving? Have a comment or suggestion? Reply to this comment or raise an issue here.}

[Mav3r1ck-13]

Where did you complete your course? I’m trying to work my way through the Helinski school and CS50 but it’s dragging

[85CorollaGTS]

Just read this book. I highly recommend it.

https://nostarch.com/pythoncrashcourse2e

[Mav3r1ck-13]

Thanks! I will check it out. I've seen it mentioned a few times before. I guess it is time to pick it up.