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@ -8,9 +8,9 @@ |
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Several versions of the Python interpreter are available on Nix, as well as a |
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high amount of packages. The attribute `python3` refers to the default |
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interpreter, which is currently CPython 3.9. The attribute `python` refers to |
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interpreter, which is currently CPython 3.10. The attribute `python` refers to |
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CPython 2.7 for backwards-compatibility. It is also possible to refer to |
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specific versions, e.g. `python38` refers to CPython 3.8, and `pypy` refers to |
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specific versions, e.g. `python39` refers to CPython 3.9, and `pypy` refers to |
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the default PyPy interpreter. |
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Python is used a lot, and in different ways. This affects also how it is |
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@ -26,10 +26,10 @@ however, are in separate sets, with one set per interpreter version. |
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The interpreters have several common attributes. One of these attributes is |
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`pkgs`, which is a package set of Python libraries for this specific |
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interpreter. E.g., the `toolz` package corresponding to the default interpreter |
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is `python.pkgs.toolz`, and the CPython 3.8 version is `python38.pkgs.toolz`. |
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is `python.pkgs.toolz`, and the CPython 3.9 version is `python39.pkgs.toolz`. |
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The main package set contains aliases to these package sets, e.g. |
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`pythonPackages` refers to `python.pkgs` and `python38Packages` to |
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`python38.pkgs`. |
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`pythonPackages` refers to `python.pkgs` and `python39Packages` to |
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`python39.pkgs`. |
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#### Installing Python and packages {#installing-python-and-packages} |
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@ -54,7 +54,7 @@ with `python.buildEnv` or `python.withPackages` where the interpreter and other |
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executables are wrapped to be able to find each other and all of the modules. |
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In the following examples we will start by creating a simple, ad-hoc environment |
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with a nix-shell that has `numpy` and `toolz` in Python 3.8; then we will create |
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with a nix-shell that has `numpy` and `toolz` in Python 3.9; then we will create |
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a re-usable environment in a single-file Python script; then we will create a |
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full Python environment for development with this same environment. |
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@ -70,10 +70,10 @@ temporary shell session with a Python and a *precise* list of packages (plus |
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their runtime dependencies), with no other Python packages in the Python |
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interpreter's scope. |
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To create a Python 3.8 session with `numpy` and `toolz` available, run: |
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To create a Python 3.9 session with `numpy` and `toolz` available, run: |
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```sh |
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$ nix-shell -p 'python38.withPackages(ps: with ps; [ numpy toolz ])' |
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$ nix-shell -p 'python39.withPackages(ps: with ps; [ numpy toolz ])' |
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``` |
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By default `nix-shell` will start a `bash` session with this interpreter in our |
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@ -81,8 +81,8 @@ By default `nix-shell` will start a `bash` session with this interpreter in our |
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```Python console |
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[nix-shell:~/src/nixpkgs]$ python3 |
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Python 3.8.1 (default, Dec 18 2019, 19:06:26) |
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[GCC 9.2.0] on linux |
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Python 3.9.12 (main, Mar 23 2022, 21:36:19) |
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[GCC 11.3.0] on linux |
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Type "help", "copyright", "credits" or "license" for more information. |
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>>> import numpy; import toolz |
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``` |
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@ -102,13 +102,16 @@ will still get 1 wrapped Python interpreter. We can start the interpreter |
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directly like so: |
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```sh |
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$ nix-shell -p 'python38.withPackages(ps: with ps; [ numpy toolz requests ])' --run python3 |
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these derivations will be built: |
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/nix/store/xbdsrqrsfa1yva5s7pzsra8k08gxlbz1-python3-3.8.1-env.drv |
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building '/nix/store/xbdsrqrsfa1yva5s7pzsra8k08gxlbz1-python3-3.8.1-env.drv'... |
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created 277 symlinks in user environment |
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Python 3.8.1 (default, Dec 18 2019, 19:06:26) |
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[GCC 9.2.0] on linux |
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$ nix-shell -p "python39.withPackages (ps: with ps; [ numpy toolz requests ])" --run python3 |
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this derivation will be built: |
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/nix/store/mpn7k6bkjl41fm51342rafaqfsl10qs4-python3-3.9.12-env.drv |
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this path will be fetched (0.09 MiB download, 0.41 MiB unpacked): |
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/nix/store/5gaiacnzi096b6prc6aa1pwrhncmhc8b-python3.9-toolz-0.11.2 |
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copying path '/nix/store/5gaiacnzi096b6prc6aa1pwrhncmhc8b-python3.9-toolz-0.11.2' from 'https://cache.nixos.org'... |
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building '/nix/store/mpn7k6bkjl41fm51342rafaqfsl10qs4-python3-3.9.12-env.drv'... |
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created 279 symlinks in user environment |
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Python 3.9.12 (main, Mar 23 2022, 21:36:19) |
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[GCC 11.3.0] on linux |
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Type "help", "copyright", "credits" or "license" for more information. |
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>>> import requests |
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>>> |
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@ -147,7 +150,7 @@ Executing this script requires a `python3` that has `numpy`. Using what we learn |
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in the previous section, we could startup a shell and just run it like so: |
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```ShellSession |
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$ nix-shell -p 'python38.withPackages(ps: with ps; [ numpy ])' --run 'python3 foo.py' |
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$ nix-shell -p 'python39.withPackages(ps: with ps; [ numpy ])' --run 'python3 foo.py' |
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The dot product of [1 2] and [3 4] is: 11 |
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``` |
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@ -210,12 +213,12 @@ create a single script with Python dependencies, but in the course of normal |
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development we're usually working in an entire package repository. |
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As explained in the Nix manual, `nix-shell` can also load an expression from a |
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`.nix` file. Say we want to have Python 3.8, `numpy` and `toolz`, like before, |
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`.nix` file. Say we want to have Python 3.9, `numpy` and `toolz`, like before, |
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in an environment. We can add a `shell.nix` file describing our dependencies: |
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```nix |
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with import <nixpkgs> {}; |
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(python38.withPackages (ps: [ps.numpy ps.toolz])).env |
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(python39.withPackages (ps: [ps.numpy ps.toolz])).env |
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``` |
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And then at the command line, just typing `nix-shell` produces the same |
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@ -229,7 +232,7 @@ What's happening here? |
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imports the `<nixpkgs>` function, `{}` calls it and the `with` statement |
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brings all attributes of `nixpkgs` in the local scope. These attributes form |
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the main package set. |
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2. Then we create a Python 3.8 environment with the `withPackages` function, as before. |
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2. Then we create a Python 3.9 environment with the `withPackages` function, as before. |
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3. The `withPackages` function expects us to provide a function as an argument |
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that takes the set of all Python packages and returns a list of packages to |
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include in the environment. Here, we select the packages `numpy` and `toolz` |
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@ -240,7 +243,7 @@ To combine this with `mkShell` you can: |
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```nix |
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with import <nixpkgs> {}; |
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let |
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pythonEnv = python38.withPackages (ps: [ |
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pythonEnv = python39.withPackages (ps: [ |
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ps.numpy |
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ps.toolz |
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]); |
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@ -378,8 +381,8 @@ information. The output of the function is a derivation. |
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An expression for `toolz` can be found in the Nixpkgs repository. As explained |
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in the introduction of this Python section, a derivation of `toolz` is available |
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for each interpreter version, e.g. `python38.pkgs.toolz` refers to the `toolz` |
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derivation corresponding to the CPython 3.8 interpreter. |
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for each interpreter version, e.g. `python39.pkgs.toolz` refers to the `toolz` |
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derivation corresponding to the CPython 3.9 interpreter. |
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The above example works when you're directly working on |
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`pkgs/top-level/python-packages.nix` in the Nixpkgs repository. Often though, |
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@ -392,11 +395,11 @@ and adds it along with a `numpy` package to a Python environment. |
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with import <nixpkgs> {}; |
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( let |
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my_toolz = python38.pkgs.buildPythonPackage rec { |
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my_toolz = python39.pkgs.buildPythonPackage rec { |
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pname = "toolz"; |
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version = "0.10.0"; |
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src = python38.pkgs.fetchPypi { |
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src = python39.pkgs.fetchPypi { |
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inherit pname version; |
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sha256 = "08fdd5ef7c96480ad11c12d472de21acd32359996f69a5259299b540feba4560"; |
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}; |
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@ -414,7 +417,7 @@ with import <nixpkgs> {}; |
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``` |
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Executing `nix-shell` will result in an environment in which you can use |
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Python 3.8 and the `toolz` package. As you can see we had to explicitly mention |
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Python 3.9 and the `toolz` package. As you can see we had to explicitly mention |
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for which Python version we want to build a package. |
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So, what did we do here? Well, we took the Nix expression that we used earlier |
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@ -742,7 +745,7 @@ If we create a `shell.nix` file which calls `buildPythonPackage`, and if `src` |
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is a local source, and if the local source has a `setup.py`, then development |
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mode is activated. |
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In the following example we create a simple environment that has a Python 3.8 |
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In the following example we create a simple environment that has a Python 3.9 |
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version of our package in it, as well as its dependencies and other packages we |
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like to have in the environment, all specified with `propagatedBuildInputs`. |
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Indeed, we can just add any package we like to have in our environment to |
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@ -750,7 +753,7 @@ Indeed, we can just add any package we like to have in our environment to |
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```nix |
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with import <nixpkgs> {}; |
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with python38Packages; |
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with python39Packages; |
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buildPythonPackage rec { |
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name = "mypackage"; |
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@ -828,9 +831,9 @@ and in this case the `python38` interpreter is automatically used. |
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### Interpreters {#interpreters} |
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Versions 2.7, 3.7, 3.8 and 3.9 of the CPython interpreter are available as |
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respectively `python27`, `python37`, `python38` and `python39`. The |
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aliases `python2` and `python3` correspond to respectively `python27` and |
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Versions 2.7, 3.7, 3.8, 3.9 and 3.10 of the CPython interpreter are available |
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as respectively `python27`, `python37`, `python38`, `python39` and `python310`. |
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The aliases `python2` and `python3` correspond to respectively `python27` and |
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`python39`. The attribute `python` maps to `python2`. The PyPy interpreters |
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compatible with Python 2.7 and 3 are available as `pypy27` and `pypy3`, with |
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aliases `pypy2` mapping to `pypy27` and `pypy` mapping to `pypy2`. The Nix |
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Vladimír Čunát
2 years ago