# What Is an Editable Install?

An editable install (also called a "development install") installs a Python package so that changes to the source code are immediately reflected in the environment without requiring reinstallation. Both [pip](https://pydevtools.com/handbook/reference/pip.md) and [uv](https://pydevtools.com/handbook/reference/uv.md) support editable installs via the `-e` flag. They are for active development; do not use them in production environments.

## How Editable Installs Work

Under the hood, an editable install places a `.pth` file in the Python environment's `site-packages` directory instead of copying the package files there. That `.pth` file points Python's import system to the development directory containing the source code. Your IDE can find and interact with the actual source files.

Compiled extensions are not automatically rebuilt when you change their source. Recompile them manually after modifying C extension code.

## Caveats

- Moving or renaming the source directory breaks the `.pth` pointer silently; reinstall with `-e` after any such move.
- Data files and package resources may resolve to source-tree paths rather than installed paths. Verify the behavior with a real wheel install before publishing.

## How PEP 660 Standardized Editable Installs

[PEP 660](https://pydevtools.com/handbook/explanation/what-is-pep-660.md) introduced a standard hook API that any [PEP 517](https://pydevtools.com/handbook/explanation/what-is-pep-517.md)-compliant [build backend](https://pydevtools.com/handbook/explanation/what-is-a-build-backend.md) can implement to support editable installs. Before PEP 660, editable installs were only available through [setuptools](https://pydevtools.com/handbook/reference/setuptools.md)' `setup.py develop` command. The PEP decoupled this workflow from setuptools, allowing backends like [Hatch](https://pydevtools.com/handbook/reference/hatch.md) and [Flit](https://pydevtools.com/handbook/reference/flit.md) to support editable installs through a common interface.

## Learn More

* [What is PEP 660?](https://pydevtools.com/handbook/explanation/what-is-pep-660.md) covers the standard that decoupled editable installs from setuptools
* [What is a build backend?](https://pydevtools.com/handbook/explanation/what-is-a-build-backend.md) explains the systems that implement editable installs
* [PEP 660 — Editable installs for pyproject.toml based builds](https://peps.python.org/pep-0660/)