Interview Q&A / Object-Oriented Programming

1. How would you build a simple factory in Python without a long if-elif chain?

   Keep a dictionary that maps names to classes and look the class up. Adding a new type is a one-line registration rather than another elif branch.

   IntermediateQuick answer1 min read
2. What is the difference between the Factory Method and Abstract Factory patterns?

   Factory Method lets a subclass decide which single product to create. Abstract Factory creates a whole family of related products that are meant to be used together.

   IntermediateQuick answer1 min read
3. What is the difference between the Observer pattern and Publish-Subscribe?

   In Observer, observers register directly with the subject and the subject calls them. In Pub-Sub, a message broker sits between publishers and subscribers, so neither knows the other.

   IntermediateQuick answer1 min read
4. Why do many developers call Singleton an anti-pattern?

   It is global state in disguise: hidden dependencies, hard-to-reset state between tests, tight coupling to one concrete class, and trouble when you later need two instances.

   IntermediateQuick answer1 min read