Calling update functions in class __init__(): Proper Style?

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#1

Hello,
I am currently working on my own project, and wanted to create a class that represents a bug.
I wrote the function .update_prority(new_priority) that updates the instance variable self.priority. It also checks if is withing a range of allowed priorities.
To do this check, I call the .update_priority function within the init() function.
After that worked, I thought why not assign all instance variables via the update function. That case, if I have checks later on they are automatically run later down the road.

This is my class so far:

class Bug: instance_counter = 1 allowed_priorities = ["Low", "Middle", "High"] def __init__(self, title="Title", description="Description", priority="Middle", category=None): self.update_title(title) self.update_description(description) self.update_priority(priority) self.id = Bug.instance_counter #assign a unique id to each the bug Bug.instance_counter+=1 #update the title def update_title(self, new_title): self.title = new_title def update_description(self, new_description): self.description = new_description # updates priority if the priority is in Tuple of allowed priorities def update_priority(self, new_priority): if new_priority in Bug.allowed_priorities: self.priority = new_priority else: raise ValueError("Priority can only be Low, Middle or High") def updated_category(self, new_category): self.category = new_category new_bug = Bug("Title 1", "Description", "Middle") new_bug2 = Bug("Title 2", "Desc", "Low") print(new_bug2.priority) print(new_bug2.title) print(new_bug2.id)

I added some execution code as an example as well.

My Question:
I know it is working, but is it allowed under style guidelines?
Can there be any issues down the road with this implementation?

#2

If you’re adding validation to the members of the class then what you’re suggesting does make sense and is one of the arguments for using the Mutator method - Wikipedia (setters). However Python normally avoids this pattern and instead a Property (programming) - Wikipedia is often suggested. See the docs https://docs.python.org/3/library/functions.html#property for details on a built-in tool designed for this purpose.

One thing you could look into is separating the validation from the class itself, especially since you’re not certain what validation you actually need at this point. If you have a search around for OOP design patterns for validation you might find some nice ideas for this (there’s various options). The docs on Python descriptors might give you a few ideas too e.g. https://docs.python.org/3.10/howto/descriptor.html#complete-practical-example. This is a bit more complex than property but potentially offers a little more flexibility without directly altering the original class; worth a quick look anyway.

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#3

Thanks for the hints! I will have another look at this topic and the classes. Feels like I didn’t fully grasp it yet, but great exercise to learn

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#4

A lot of the OOP things take a long time to sink in (along with practice and use) but it sounds like you’re thinking about it the right way anyway which is definitely a good thing :+1:. I’m not sure codecademy introduces property in the course (perhaps briefly in one the advanced python topics) nor general design patterns so you might need to hunt elsewhere.

If you’re still new to using classes in general then I wouldn’t worry too much about them right now. They’re designed to make OOP development easier in the long term, I think getting used to classes and objects is a good idea and then you can worry about design patterns and so on.