All Questions
Tagged with python object-oriented
156 questions
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32
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API design for precomputation cache [closed]
In my numeric code library I have a function totient_sum that depends on an expensive one-time precomputation totsum_range = [...], then different calls to totient_sum(n) are quick. There are several ...
- 342
0
votes
1
answer
258
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Separation of concerns between business layer, data layer and presentation layer without losing information
I'm developing an api in Fast API using sqlalchemy to manage my ORM classes and operations with the database.
I'm dealing with some design decisions to have my classes as little coupled as possible ...
2
votes
1
answer
1k
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In Python when is absolutely preferable to use a class instead of a module?
Python is the language I use most in this period.
My background in Java
Before start learning Python I have programmed in Java language. In Java all code is written inside the methods of a class and ...
- 171
2
votes
1
answer
146
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Refactoring Processor classes
I am writing some python 3 bioinformatics software and was wondering about the best way to write it in an OOP format. I am pretty sure a lot of my classes are violating the SRP principle, but I'm not ...
- 177
-3
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2
answers
278
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Polymorphism with variable default argument count
I'm in the process of writing a library in Python, and I've run into a design problem concerning the use of polymorphism.
I have an ABC with abstract method 'foo':
class A(ABC):
@abstractmethod
...
- 105
1
vote
3
answers
988
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Storing multiple instances on a Singleton?
RefactoringGuru's example Singleton in Python has an _instances dictionary field
class Singleton(type):
_instances = {}
def __call__(cls, *args, **kwargs):
if cls not in cls....
- 145
-2
votes
1
answer
295
views
Defining functions inside vs outside a class
Say I have a class with a function do_thing that is comprised of multiple steps, which themselves segregate into functions (first_process and second_process). At what point would this be considered ...
- 177
0
votes
1
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852
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Abstract base classes and mix-ins in python
In the python docs, I read this about the ABC (abstract base class) meta class:
Use this metaclass to create an ABC. An ABC can be subclassed directly, and then acts as a mix-in class.
I don't come ...
- 119
2
votes
2
answers
2k
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Why access the attributes of a Python class by reference?
Attribute references and instantiation
In this link, that is part of the official Python documentation, I have found the following information:
Class objects support two kinds of operations: ...
- 171
54
votes
5
answers
40k
views
Are Python mixins an anti-pattern?
I'm fully aware that pylint and other static analysis tools are not all-knowing, and sometimes their advice must be disobeyed. (This applies for various classes of messages, not just conventions.)
If ...
- 734
21
votes
3
answers
24k
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Why do you need "self." in Python to refer to instance variables?
I have been programming into a number of languages like Java, Ruby, Haskell and Python. I have to switch between many languages per day due to different projects I work on. Now, the issue is I often ...
- 473
15
votes
3
answers
3k
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The Liskov Substitution Principle, and Python
Background
I've taught myself Python over the past year-and-a-bit, and would consider myself an intermediate Python user at this point, but never studied computing at school/university. As such, my ...
- 328
3
votes
3
answers
315
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Referencing transient class attributes
I've just started dipping my feet into OOP.
Is it considered bad practice to have classes that reference attributes that depend on another function being called and thus may not exist (version 1)? I'...
- 177
-1
votes
1
answer
3k
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Calling helper functions in a Python `__init__` function
Problem
I am currently working with a class that necessarily has a very complicated initialization function (>350 lines of code) given that many computations and attributes need to be performed and ...
- 123
14
votes
3
answers
41k
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Python classes with only one instance: When to create a (single) class instance and when to work with the class instead?
Given a Python class which will be instantiated only once, i.e. there will be only one object of the class. I was wondering in which cases it makes sense to create a single class instance instead of ...
- 261