What are modules and packages, and how does import work?
⚡ Short Answer
A module is a single .py file; a package is a folder of modules (traditionally with __init__.py). `import` runs the module once and caches it in sys.modules, so re-imports are cheap. Use `if __name__ == '__main__':` to separate 'run as script' code from 'imported as a module' code.
☕Coffee Chat Question
Concept Made Simple
“What are modules and packages, and how does import work?”
🧠Mind Map Answer
Remember It Faster
⌨️Hands-on Keyboard
Learn by Doing
# mymath.py
def add(a, b):
return a + b
if __name__ == "__main__":
print(add(2, 3)) # only when run directly
# other.py
from mymath import add
print(add(10, 5)) # import doesn't run the __main__ block15
🔥What If?
Think Beyond the Expected
What is the point of `if __name__ == '__main__':`?
It lets a file work both as a runnable script and an importable module. When run directly, __name__ is '__main__' and the block executes; when imported, __name__ is the module name, so that block is skipped — preventing your test/CLI code from firing on import.
😂Real World
Every project is organized into modules/packages; the `__main__` guard is why importing a utility file doesn't accidentally run its demo code — a detail interviewers check that beginners often miss.
🎯Interviewer's Expectation
Keywords they're listening for:
⚠️Common Mistakes
- ✗Naming a file the same as a stdlib module (shadowing)
- ✗Wildcard `from x import *`
- ✗Creating circular imports
✅Best Practices
- ✓Guard script code with `if __name__ == '__main__'`
- ✓Prefer explicit imports over `import *`
- ✓Keep packages cohesive; avoid circular deps
🔁Follow-up Questions
- 1Absolute vs relative imports?
- 2What causes a circular import and how do you fix it?
- 3How does Python find modules (sys.path)?
🧩Related Technologies
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Plain-language foundations
I'm preparing for a software engineering interview and want to understand this from scratch, as a beginner. Topic: Modules (Python) Interview question: "What are modules and packages, and how does import work?" Please: 1. Explain the core idea in simple, plain language, using an everyday analogy. 2. Define any technical terms you use. 3. Walk through one small, concrete example. 4. Finish with a single sentence I can easily remember. Keep the tone friendly and assume I'm new to this topic.
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