Python: Difference between revisions

m shows instructions on how to obtain a CPython interpreter that uses debug build, related to this new PR: https://github.com/NixOS/nixpkgs/pull/409943
Lukeb (talk | contribs)
fixed broken link for pyproject use-cases
 
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</syntaxhighlight>
</syntaxhighlight>


==== Using <code>buildFHSEnv</code> ====
==== Using <code>buildFHSEnv</code> (Recommended) ====
<syntaxhighlight lang="nix">
<syntaxhighlight lang="nix">
#!/usr/bin/env nix-shell
#!/usr/bin/env nix-shell
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=== Using uv ===
=== Using uv ===
<blockquote>A single tool to replace <code>pip</code>, <code>pip-tools</code>, <code>pipx</code>, <code>poetry</code>, <code>pyenv</code>, <code>virtualenv</code>, and more.</blockquote>uv is very simple to use. Simply <code>uv init</code> to get started. No need for shells, as it creates virtual environments.
<blockquote>A single tool to replace <code>pip</code>, <code>pip-tools</code>, <code>pipx</code>, <code>poetry</code>, <code>pyenv</code>, <code>virtualenv</code>, and more.</blockquote>


As a systemPackage<syntaxhighlight lang="nix">
uv is written in Rust and does ''not'' need Python as a prerequisite. Use the <code>uv</code> command to initialize Python projects, add Python packages, create or update virtual environments (in <code>.venv</code> folders), etc. as [https://docs.astral.sh/uv/concepts/projects/ described in the uv docs]. Use uv's [https://docs.astral.sh/uv/guides/tools/ tool interface] to install and run Python packages that provide a CLI.
 
As a system package
 
<syntaxhighlight lang="nix">
environment.systemPackages = with pkgs; [
environment.systemPackages = with pkgs; [
     uv
     uv
];
];
</syntaxhighlight>or as a home-manager package<syntaxhighlight lang="nix">
</syntaxhighlight>
 
or as a home-manager package
 
<syntaxhighlight lang="nix">
home.packages = with pkgs; [
home.packages = with pkgs; [
     uv
     uv
];
];
</syntaxhighlight>
</syntaxhighlight>
If you use uv it's recommended that you install the Python versions you need using the <code>uv python install</code> command, e.g.
<syntaxhighlight lang="python">
uv python install 3.14 --preview --default
</syntaxhighlight>
You may want to set the <code>UV_PYTHON_DOWNLOADS=never</code> environment variable in your shell to stop uv from downloading Python binaries automatically if needed. Setting <code>environment.localBinInPath = true;</code> is highly recommended, because uv will install binaries in <code>~/.local/bin</code>.


=== Using poetry ===
=== Using poetry ===
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if __name__ == '__main__':
if __name__ == '__main__':
     app.run(host="0.0.0.0", port=8080)
     app.run(host="0.0.0.0", port=8080)
</syntaxhighlight>Also, you need to define the <code>pyproject.toml</code>. Here, we only show some of the important parts. Please refer to <code>pyproject.nix</code> [https://nix-community.github.io/pyproject.nix/use-cases/pyproject.html documentation] for a full example.<syntaxhighlight lang="toml">
</syntaxhighlight>Also, you need to define the <code>pyproject.toml</code>. Here, we only show some of the important parts. Please refer to <code>pyproject.nix</code> [https://pyproject-nix.github.io/pyproject.nix/use-cases/pyproject.html documentation] for a full example.<syntaxhighlight lang="toml">
[project]
[project]
name = "my-app"
name = "my-app"
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See [https://docs.python.org/3/using/configure.html#python-debug-build python wiki on debug build].
See [https://docs.python.org/3/using/configure.html#python-debug-build python wiki on debug build].


In order to use a CPython interpreter built using `--with-pydebug` during configure phase, override any of the python packages passing `enableDebug = true` argument:
In order to use a CPython interpreter built using <code>--with-pydebug</code> during configure phase, override any of the python packages passing <code>enableDebug = true</code> argument:


<code>pythonDebug = pkgs.python310.override { enableDebug = true; };</code>
<code>pythonDebug = pkgs.python310.override { enableDebug = true; };</code>
== Installing Multiple Versions ==
{{Nixpkgs Manual|name={{ic|lib.meta.lowPrio}} and {{ic|lib.meta.highPrio}}|anchor=#function-library-lib.meta.lowPrio}} can be used to install multiple versions without conflicts ({{issue|369997}}):
{{file|/etc/nixos/configuration.nix|nix|3=
environment.systemPackages = with pkgs; [
    python313
    lib.meta.lowPrio python314
];
}}
In this case you may run Python 3.13 via {{ic|python}} or {{ic|python3.13}} and Python 3.14 via {{ic|python3.14}}.
{{Note|If you wrapped Python as described in [[#Running_Python_packages_which_requires_compilation_and/or_contains_libraries_precompiled_without_nix]], call {{ic|lib.meta.lowPrio}} and {{ic|lib.meta.highPrio}} for the wrapped Python instead of calling them inside the wrapping.}}


== Performance ==
== Performance ==