uv/docs/guides/scripts.md

Running scripts

A Python script is a file intended for standalone execution, e.g., with python <script>.py. Using uv to execute scripts will ensure that script dependencies are properly managed inside and outside of projects.

Running a script without dependencies

If a script has no dependencies, it can be executed with uv run:

print("Hello world")

$ uv run example.py
Hello world

Similarly, if the script depends on a module in the standard library, there's nothing more to do:

import os

print(os.path.expanduser("~"))

$ uv run example.py
/Users/astral

Arguments can be passed to the script:

import sys

print(" ".join(sys.argv[1:]))

$ uv run example.py test
test

$ uv run example.py hello world!
hello world!

Note that if uv run is used in a project, i.e. a directory with a pyproject.toml, it will install the current project before running the script. If the script does not depend on the project, use the --isolated flag to skip this:

# Note, it is important that the flag comes _before_ the script
$ uv run --isolated example.py

See the projects guide for more details on working in projects.

Running a script with dependencies

When a script requires dependencies, they must be installed into the environment that the script runs in. uv prefers to create these environments on-demand instead of maintaining a long-lived virtual environment with manually managed dependencies. This requires explicit declaration of dependencies that are required for the script. Generally, it's recommended to use a project or inline metadata to declare dependencies, but uv supports requesting dependencies per invocation as well.

For example, the following script requires rich.

import time
from rich.progress import track

for i in track(range(20), description="For example:"):
    time.sleep(0.05)

If executed without specifying a dependency, this script will fail:

$ uv run --isolated example.py
Traceback (most recent call last):
  File "/Users/astral/example.py", line 2, in <module>
    from rich.progress import track
ModuleNotFoundError: No module named 'rich'

The dependency can be requested with the --with option:

$ uv run --with rich example.py
For example: ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 0:00:01

Constraints can be added to the requested dependency if specific versions are needed:

$ uv run --with 'rich>12,<13' example.py

Multiple dependencies can be requested by repeating with --with option.

Note that if uv run is used in a project, these dependencies will be included in addition to the project's dependencies. To opt-out of this behavior, use the --isolated flag.

Declaring script dependencies

Python recently added a standard format for inline script metadata. This allows the dependencies for a script to be declared in the script itself.

To use inline script metadata, include a script section at the top of the script:

# /// script
# dependencies = [
#   "requests<3",
#   "rich",
# ]
# ///

import requests
from rich.pretty import pprint

resp = requests.get("https://peps.python.org/api/peps.json")
data = resp.json()
pprint([(k, v["title"]) for k, v in data.items()][:10])

uv will automatically create an environment with the dependencies necessary to run the script, e.g.:

$ uv run example.py
[
│   ('1', 'PEP Purpose and Guidelines'),
│   ('2', 'Procedure for Adding New Modules'),
│   ('3', 'Guidelines for Handling Bug Reports'),
│   ('4', 'Deprecation of Standard Modules'),
│   ('5', 'Guidelines for Language Evolution'),
│   ('6', 'Bug Fix Releases'),
│   ('7', 'Style Guide for C Code'),
│   ('8', 'Style Guide for Python Code'),
│   ('9', 'Sample Plaintext PEP Template'),
│   ('10', 'Voting Guidelines')
]

uv also supports Python version requirements:

# /// script
# requires-python = ">=3.12"
# dependencies = []
# ///

# Use some syntax added in Python 3.12
type Point = tuple[float, float]
print(Point)

uv will fetch the required Python version if it is not installed — see the documentation on Python versions for more details. Note that the dependencies field must be provided even if empty.

Note that when using inline script metadata, even if uv run is used in a project, the project's dependencies will be ignored. The --isolated flag is not required.

Using different Python versions

uv allows arbitrary Python versions to be requested on each script invocation, for example:

import sys

print(".".join(map(str, sys.version_info[:3])))

# Use the default Python version, may differ on your machine
$ uv run example.py
3.12.1

# Use a specific Python version
$ uv run --python 3.10 example.py
3.10.13

See the Python versions documentation for more details on requesting Python versions.