Both uv and venv are used for managing Python virtual environments, but they are not the same. Let me break it down clearly:

1. venv (built-in Python module)

What it is: A standard library module that comes with Python (since Python 3.3).
Purpose: Creates isolated environments where you can install packages without affecting the system Python.

Command example:

  python -m venv myenv
  source myenv/bin/activate   # (Linux/Mac)
  myenv\Scripts\activate      # (Windows)

Features:
- Lightweight and built into Python.
- Doesn’t manage dependencies efficiently (you usually need pip + requirements.txt).
- No built-in lockfile mechanism.

2. uv (from Astral, 2024+)

What it is: A fast Python package and environment manager (a new alternative to pip, poetry, conda, etc.).
Purpose: Not just creating virtual environments but also managing dependencies, lockfiles, and reproducible builds.

Command example:

  uv venv myenv      # create a virtual environment
  uv pip install numpy

Features:
- Much faster than pip and venv (written in Rust).
- Built-in dependency resolver (like Poetry).
- Uses lockfiles for reproducibility.
- Can replace pip, venv, pip-tools, and even poetry in many workflows.
- Cross-platform and modern.

👉 In short:

Use venv if you just want a basic, built-in way to create a virtual environment.
Use uv if you want a modern, faster, all-in-one package & environment manager with reproducibility.