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Modules & Packages

Importing Modules

import, from, as statements for using external code

Interview: Common interview topic — circular imports and import styles are frequently discussed

Last Updated: June 12, 2026 • 9 min read

Python's import system allows you to use code from other files and libraries. Understanding import styles, module resolution, and best practices is essential for writing well-organized Python programs and is frequently tested in interviews.

Import Styles

  • import module: import os — access via os.path (recommended for clarity)
  • from module import name: from os import path — access directly as path
  • import module as alias: import numpy as np — standard convention for common libraries
  • from module import *: from math import * — imports all public names; AVOID in production code

Import Resolution Order

  • Built-in modules: Checked first (sys, os, math)
  • sys.path directories: Current directory, then PYTHONPATH, then standard library paths
  • Installed packages: From site-packages (pip-installed packages)

Avoid Wildcard Imports

from module import * pollutes the namespace, makes it unclear where names come from, and can override built-in functions. Always use explicit imports. PEP 8 allows it only in interactive shells and __init__.py for re-exporting.

Circular Imports

When module A imports module B, and module B imports module A, you get a circular import. Python handles this partially (the module exists but may be incomplete), but it causes subtle bugs. Solutions: restructure code, use local imports inside functions, or merge the modules.

PEP 8 Import Rules

Imports should be at the top of the file, grouped in this order: (1) standard library, (2) third-party, (3) local. Each group separated by a blank line. Use one import per line for clarity.

Use Cases

Organizing code across multiple files with clean import patterns

Using standard library and third-party packages effectively

Lazy loading optional dependencies with try/except ImportError

Building package APIs with __init__.py re-exports

Avoiding circular dependencies in large codebases

Common Mistakes

Using from module import * — pollutes namespace, hides name origins, can override builtins

Not following PEP 8 import ordering — makes code harder to scan

Ignoring circular imports — causes incomplete module loading and subtle bugs

Importing at function level when top-level import would work — unnecessary complexity

Forgetting that imports are executed only once — module-level code runs on first import