Reloading modules in Python

Last Updated : 21 Jun, 2025

We are given a case where we want to update and test a Python module without restarting the interpreter. This is especially helpful during development when you're modifying module files externally and want those changes to reflect immediately. Python allows us to reload a previously imported module using the reload() function. For example, if you've edited a utility file utils.py while your script is running, reloading lets you re-import the updated content without restarting the Python shell.

When Should You Reload a Module?

During debugging or live testing
When using interactive interpreters like IPython or Jupyter
While developing plugins or modular systems
To reflect changes made in external .py files without restarting the session

Reloading Modules in Python 2.x

In Python 2.x, you can directly use the built-in reload() function to reload a module that was previously imported.

Python

import mymodule

# Modify 'mymodule.py' externally here...

reload(mymodule)

Explanation:

mymodule is first imported using import.
After making external changes to mymodule.py, calling reload(mymodule) reloads the updated version without restarting the interpreter.
No need to re-import — reload() works on an already imported module object.

Reloading Modules in Python 3.0 to 3.3

In Python versions 3.0 to 3.3, the built-in reload() function was removed. Instead, you need to import it from the imp module.

Python

import mymodule
import imp

# Modify 'mymodule.py' externally...

imp.reload(mymodule)

Explanation:

First, mymodule is imported as usual.
The imp module provides the reload() function during this version range.
After editing mymodule.py, imp.reload(mymodule) reloads the module with updated changes.

Note: The imp module is deprecated as of Python 3.4 and is replaced by importlib.

Reloading Modules in Python 3.4 and Above

Starting from Python 3.4, the recommended way to reload a module is by using importlib.reload().

Python

import mymodule
import importlib

# Modify 'mymodule.py' externally...

importlib.reload(mymodule)

Explanation:

mymodule is first imported normally.
Then, importlib.reload(mymodule) reloads the updated module.
This is the current and official way to reload modules in Python 3.4+.

Note: Use this method in all modern Python scripts and notebooks when testing module changes.

Can You Unload a Module in Python?

Currently, Python does not provide a built-in way to fully unload a module once it's imported. Once a module is loaded into memory, it stays available in sys.modules until the program ends. Although you can delete a module from sys.modules, this doesn't guarantee its complete removal from memory or that its references are gone:

Python

import mymodule
import sys

del sys.modules['mymodule']

This will only remove the module from the sys.modules cache. If any variable or object is still referencing the module, it won’t be fully unloaded.

Why Unloading Isn’t Supported?

Python manages modules globally in memory.
Unloading dynamically could lead to inconsistent behavior if parts of your code still hold references to the old module.