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⭐ Path Searching of a Module in Python

When you import a module in Python—like:

import math
import mymodule

Python must locate the module file.
The process through which Python searches for modules is called the Module Search Path.

Python follows a specific order to find modules, defined by the module search path list, stored in:

sys.path

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⭐ How Python Searches for a Module (Order of Search)

Python searches for a module in the following sequence:

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1️⃣ Current Working Directory (CWD)

Python first looks for the module in the directory from where your program is running.

Example:
If your file main.py and mymodule.py are in the same folder:

project/
   main.py
   mymodule.py

Then:

import mymodule

Python finds it instantly.

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2️⃣ PYTHONPATH Environment Variable

If the module isn’t found in CWD, Python checks PYTHONPATH, which is an environment variable containing extra module directories.

To view PYTHONPATH:

import os
print(os.environ.get("PYTHONPATH"))

You can add custom directories here.

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3️⃣ Standard Library Directories

Python checks the folders where built-in modules are stored.

Example modules found here:

• math
• os
• random
• datetime

These are installed with Python itself.

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4️⃣ Site-packages Directory (Third-party Modules)

Python next checks the directory where external modules (installed via pip) are stored.

Example:

• numpy
• pandas
• requests
• matplotlib

Typically located at:

C:\Python\Lib\site-packages\

or in Linux:

/usr/local/lib/python3.x/site-packages/

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5️⃣ Built-in Module Registry

Finally, Python checks its built-in module dictionary for modules written in C.

Examples:

• sys
• time
• itertools

If still not found:
👉 Python raises ModuleNotFoundError

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⭐ Viewing Python’s Module Search Path

Use:

import sys
print(sys.path)

This prints a list of directories that Python searches for modules.

Example Output:

[
 'C:\\Users\\User\\Project',
 'C:\\Python39\\python39.zip',
 'C:\\Python39\\DLLs',
 'C:\\Python39\\lib',
 'C:\\Python39',
 'C:\\Python39\\lib\\site-packages'
]

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⭐ Modifying Module Search Path at Runtime

You can manually add a folder to the path:

import sys
sys.path.append("C:/myfolder")

Now Python will search this folder too.

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⭐ Why Understanding Module Search Path Is Important?

✔ Helps solve ModuleNotFoundError
✔ Required when using custom modules
✔ Useful when installing third-party libraries
✔ Helps organize large Python projects
✔ Required for interview & university exams

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⭐ Exam-Ready Answer (Short Form)

Python searches for a module using the module search path defined in sys.path. The search order is: (1) Current Working Directory, (2) PYTHONPATH environment variable, (3) Standard Library directories, (4) Site-packages, and (5) Built-in module registry. If the module is not found in any of these, Python raises ModuleNotFoundError.

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