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128 lines
4.7 KiB
Markdown
128 lines
4.7 KiB
Markdown
# Installing Python
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If Python is already installed on your system, uv will
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[detect and use](#using-an-existing-python-installation) it without configuration. However, uv can
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also install and manage Python versions for you.
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!!! tip
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uv will [automatically fetch Python versions](#automatic-python-downloads) as needed — you don't need to install Python to get started.
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<!-- TODO(zanieb): I don't love this heading. -->
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## Getting started
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To install the latest Python version:
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```console
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$ uv python install
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```
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This will install a uv-managed Python version even if there is already a Python installation on your
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system. If you've previously installed Python with uv, a new version will not be installed.
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!!! note
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Python does not publish official distributable binaries. As such, uv uses third-party distributions from the [`python-build-standalone`](https://github.com/indygreg/python-build-standalone) project. The project is partially maintained by the uv maintainers and is used by other prominent Python projects (e.g., [Rye](https://github.com/astral-sh/rye), [Bazel](https://github.com/bazelbuild/rules_python)). See the [Python distributions](../concepts/python-versions.md#managed-python-distributions) documentation for more details.
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<!-- TODO(zanieb): Restore when Python shim management is added
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Note that when an automatic Python installation occurs, the `python` command will not be added to the shell. Use `uv python install-shim` to ensure the `python` shim is installed.
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Once Python is installed, it can be invoked via `python`:
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```console
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$ python --version
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```
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To prevent uv from managing Python system-wide, provide the `--no-shim` option during installation.
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-->
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Once Python is installed, it will be used by `uv` commands automatically.
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!!! important
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When Python is installed by uv, it will not be available globally (i.e. via the `python` command).
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Support for this feature is planned for a future release. In the meantime, use
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[`uv run`](../guides/scripts.md#using-different-python-versions) or
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[create and activate a virtual environment](../pip/environments.md) to use `python` directly.
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## Installing a specific version
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To install a specific Python version:
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```console
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$ uv python install 3.12
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```
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To install multiple Python versions:
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```console
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$ uv python install 3.11 3.12
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```
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To install an alternative Python implementation, e.g. PyPy:
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```console
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$ uv python install pypy@3.12
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```
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See the [`python install`](../concepts/python-versions.md#installing-a-python-version) documentation
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for more details.
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## Viewing Python installations
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To view available and installed Python versions:
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```console
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$ uv python list
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```
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See the [`python list`](../concepts/python-versions.md#viewing-available-python-versions)
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documentation for more details.
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<!--TODO(zanieb): The above should probably link to a CLI reference and that content should be moved out of that file -->
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## Automatic Python downloads
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Note that Python does not need to be explicitly installed to use uv. By default, uv will
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automatically download Python versions when they are required. For example, the following would
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download Python 3.12 if it was not installed:
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```console
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$ uv run --python 3.12 python -c 'print("hello world")'
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```
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Even if a specific Python version is not requested, uv will download the latest version on demand.
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For example, the following will create a new virtual environment and download a managed Python
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version if Python is not found:
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```console
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$ uv venv
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```
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!!! tip
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Automatic Python downloads can be [easily disabled](../concepts/python-versions.md#disabling-automatic-python-downloads) if you want more control over when Python is downloaded.
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<!-- TODO(zanieb): Restore when Python shim management is added
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Note that when an automatic Python installation occurs, the `python` command will not be added to the shell. Use `uv python install-shim` to ensure the `python` shim is installed.
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-->
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## Using an existing Python installation
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uv will use existing Python installations if present on your system. There is no configuration
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necessary for this behavior: uv will use the system Python if it satisfies the requirements of the
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command invocation. See the
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[Python discovery](../concepts/python-versions.md#discovery-of-python-versions) documentation for
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details.
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To force uv to use the system Python, provide the `--python-preference only-system` option. See the
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[Python version preference](../concepts/python-versions.md#adjusting-python-version-preferences)
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documentation for more details.
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## Next steps
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To learn more about `uv python`, see the [Python version concept](../concepts/python-versions.md)
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page and the [command reference](../reference/cli.md#uv-python).
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Or, read on to learn how to [run scripts](./scripts.md) and invoke Python with uv.
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