Design patterns — Python Technical Interview Questions & Answers

Design patterns

Design patterns

  • Design patterns is a practical Python topic. Explain the job in school English, then the first three steps you would actually do.
  • Design patterns in practice: Pygame = game loop + window. CGI = old web scripts (today: Flask). Design patterns = reusable class shapes (singleton, factory) — only when the problem needs them. Deploy = put the script on Linux/Windows with venv + a start command. IDE = VS Code / PyCharm to edit and run.
  • For Design patterns always: venv, requirements.txt, don’t commit secrets.
  • Design patterns — output: True. Singleton — one instance. Only use a pattern when the problem needs it.

Technical Interview Tip: Job in one line + three steps.

Code Examples for Design patterns

Example

# Design patterns
class School:
    _one = None
    def __new__(cls):
        if cls._one is None:
            cls._one = super().__new__(cls)
        return cls._one
print(School() is School())

Design patterns — output: True. Singleton — one instance. Only use a pattern when the problem needs it.

How to Explain Design patterns to an Interviewer

Explain Design patterns as if you are teaching a junior — definition, then one tiny script.

Design patterns — practical job. Design patterns — three real steps.

What does the example print, and why?

Design patterns — output: True

What mistake do freshers make with Design patterns?

Design patterns needs venv + requirements.