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doc: update python manual to reference python 3.8 instead of 3.5 

Improvement suggested in #87094
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Benjamin Hipple 2020-05-09 12:58:00 -04:00
parent d4c2f1ab5d
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doc/languages-frameworks/python.section.md
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@ -9,7 +9,7 @@
Several versions of the Python interpreter are available on Nix, as well as a Several versions of the Python interpreter are available on Nix, as well as a
high amount of packages. The attribute `python` refers to the default high amount of packages. The attribute `python` refers to the default
interpreter, which is currently CPython 2.7. It is also possible to refer to interpreter, which is currently CPython 2.7. It is also possible to refer to
specific versions, e.g. `python35` refers to CPython 3.5, and `pypy` refers to specific versions, e.g. `python38` refers to CPython 3.8, and `pypy` refers to
the default PyPy interpreter. the default PyPy interpreter.
Python is used a lot, and in different ways. This affects also how it is Python is used a lot, and in different ways. This affects also how it is
@ -25,10 +25,10 @@ however, are in separate sets, with one set per interpreter version.
The interpreters have several common attributes. One of these attributes is The interpreters have several common attributes. One of these attributes is
`pkgs`, which is a package set of Python libraries for this specific `pkgs`, which is a package set of Python libraries for this specific
interpreter. E.g., the `toolz` package corresponding to the default interpreter interpreter. E.g., the `toolz` package corresponding to the default interpreter
is `python.pkgs.toolz`, and the CPython 3.5 version is `python35.pkgs.toolz`. is `python.pkgs.toolz`, and the CPython 3.8 version is `python38.pkgs.toolz`.
The main package set contains aliases to these package sets, e.g. The main package set contains aliases to these package sets, e.g.
`pythonPackages` refers to `python.pkgs` and `python35Packages` to `pythonPackages` refers to `python.pkgs` and `python38Packages` to
`python35.pkgs`. `python38.pkgs`.
#### Installing Python and packages #### Installing Python and packages
@ -50,7 +50,7 @@ to create an environment with `python.buildEnv` or `python.withPackages` where
the interpreter and other executables are able to find each other and all of the the interpreter and other executables are able to find each other and all of the
modules. modules.
In the following examples we create an environment with Python 3.5, `numpy` and In the following examples we create an environment with Python 3.8, `numpy` and
`toolz`. As you may imagine, there is one limitation here, and that's that `toolz`. As you may imagine, there is one limitation here, and that's that
you can install only one environment at a time. You will notice the complaints you can install only one environment at a time. You will notice the complaints
about collisions when you try to install a second environment. about collisions when you try to install a second environment.
@ -61,7 +61,7 @@ Create a file, e.g. `build.nix`, with the following expression
```nix ```nix
with import <nixpkgs> {}; with import <nixpkgs> {};
python35.withPackages (ps: with ps; [ numpy toolz ]) python38.withPackages (ps: with ps; [ numpy toolz ])
``` ```
and install it in your profile with and install it in your profile with
```shell ```shell
@ -79,7 +79,7 @@ Nixpkgs set, e.g. using `config.nix`,
{ # ... { # ...
packageOverrides = pkgs: with pkgs; { packageOverrides = pkgs: with pkgs; {
myEnv = python35.withPackages (ps: with ps; [ numpy toolz ]); myEnv = python38.withPackages (ps: with ps; [ numpy toolz ]);
}; };
} }
``` ```
@ -101,7 +101,7 @@ environment system-wide.
{ # ... { # ...
environment.systemPackages = with pkgs; [ environment.systemPackages = with pkgs; [
(python35.withPackages(ps: with ps; [ numpy toolz ])) (python38.withPackages(ps: with ps; [ numpy toolz ]))
]; ];
} }
``` ```
@ -118,7 +118,7 @@ recommended method is to create an environment with `python.buildEnv` or
`python.withPackages` and load that. E.g. `python.withPackages` and load that. E.g.
```sh ```sh
$ nix-shell -p 'python35.withPackages(ps: with ps; [ numpy toolz ])' $ nix-shell -p 'python38.withPackages(ps: with ps; [ numpy toolz ])'
``` ```
opens a shell from which you can launch the interpreter opens a shell from which you can launch the interpreter
@ -131,7 +131,7 @@ The other method, which is not recommended, does not create an environment and
requires you to list the packages directly, requires you to list the packages directly,
```sh ```sh
$ nix-shell -p python35.pkgs.numpy python35.pkgs.toolz $ nix-shell -p python38.pkgs.numpy python38.pkgs.toolz
``` ```
Again, it is possible to launch the interpreter from the shell. The Python Again, it is possible to launch the interpreter from the shell. The Python
@ -140,14 +140,14 @@ that specific interpreter.
##### Load environment from `.nix` expression ##### Load environment from `.nix` expression
As explained in the Nix manual, `nix-shell` can also load an As explained in the Nix manual, `nix-shell` can also load an
expression from a `.nix` file. Say we want to have Python 3.5, `numpy` expression from a `.nix` file. Say we want to have Python 3.8, `numpy`
and `toolz`, like before, in an environment. Consider a `shell.nix` file and `toolz`, like before, in an environment. Consider a `shell.nix` file
with with
```nix ```nix
with import <nixpkgs> {}; with import <nixpkgs> {};
(python35.withPackages (ps: [ps.numpy ps.toolz])).env (python38.withPackages (ps: [ps.numpy ps.toolz])).env
``` ```
Executing `nix-shell` gives you again a Nix shell from which you can run Python. Executing `nix-shell` gives you again a Nix shell from which you can run Python.
@ -158,7 +158,7 @@ What's happening here?
imports the `<nixpkgs>` function, `{}` calls it and the `with` statement imports the `<nixpkgs>` function, `{}` calls it and the `with` statement
brings all attributes of `nixpkgs` in the local scope. These attributes form brings all attributes of `nixpkgs` in the local scope. These attributes form
the main package set. the main package set.
2. Then we create a Python 3.5 environment with the `withPackages` function. 2. Then we create a Python 3.8 environment with the `withPackages` function.
3. The `withPackages` function expects us to provide a function as an argument 3. The `withPackages` function expects us to provide a function as an argument
that takes the set of all python packages and returns a list of packages to that takes the set of all python packages and returns a list of packages to
include in the environment. Here, we select the packages `numpy` and `toolz` include in the environment. Here, we select the packages `numpy` and `toolz`
@ -170,7 +170,7 @@ To combine this with `mkShell` you can:
with import <nixpkgs> {}; with import <nixpkgs> {};
let let
pythonEnv = python35.withPackages (ps: [ pythonEnv = python38.withPackages (ps: [
ps.numpy ps.numpy
ps.toolz ps.toolz
]); ]);
@ -188,13 +188,13 @@ option, with which you can execute a command in the `nix-shell`. We can
e.g. directly open a Python shell e.g. directly open a Python shell
```sh ```sh
$ nix-shell -p python35Packages.numpy python35Packages.toolz --run "python3" $ nix-shell -p python38Packages.numpy python38Packages.toolz --run "python3"
``` ```
or run a script or run a script
```sh ```sh
$ nix-shell -p python35Packages.numpy python35Packages.toolz --run "python3 myscript.py" $ nix-shell -p python38Packages.numpy python38Packages.toolz --run "python3 myscript.py"
``` ```
##### `nix-shell` as shebang ##### `nix-shell` as shebang
@ -231,11 +231,11 @@ building Python libraries is `buildPythonPackage`. Let's see how we can build th
buildPythonPackage rec { buildPythonPackage rec {
pname = "toolz"; pname = "toolz";
version = "0.7.4"; version = "0.10.0";
src = fetchPypi { src = fetchPypi {
inherit pname version; inherit pname version;
sha256 = "43c2c9e5e7a16b6c88ba3088a9bfc82f7db8e13378be7c78d6c14a5f8ed05afd"; sha256 = "08fdd5ef7c96480ad11c12d472de21acd32359996f69a5259299b540feba4560";
}; };
doCheck = false; doCheck = false;
@ -260,8 +260,8 @@ information. The output of the function is a derivation.
An expression for `toolz` can be found in the Nixpkgs repository. As explained An expression for `toolz` can be found in the Nixpkgs repository. As explained
in the introduction of this Python section, a derivation of `toolz` is available in the introduction of this Python section, a derivation of `toolz` is available
for each interpreter version, e.g. `python35.pkgs.toolz` refers to the `toolz` for each interpreter version, e.g. `python38.pkgs.toolz` refers to the `toolz`
derivation corresponding to the CPython 3.5 interpreter. derivation corresponding to the CPython 3.8 interpreter.
The above example works when you're directly working on The above example works when you're directly working on
`pkgs/top-level/python-packages.nix` in the Nixpkgs repository. Often though, `pkgs/top-level/python-packages.nix` in the Nixpkgs repository. Often though,
you will want to test a Nix expression outside of the Nixpkgs tree. you will want to test a Nix expression outside of the Nixpkgs tree.
@ -273,13 +273,13 @@ and adds it along with a `numpy` package to a Python environment.
with import <nixpkgs> {}; with import <nixpkgs> {};
( let ( let
my_toolz = python35.pkgs.buildPythonPackage rec { my_toolz = python38.pkgs.buildPythonPackage rec {
pname = "toolz"; pname = "toolz";
version = "0.7.4"; version = "0.10.0";
src = python35.pkgs.fetchPypi { src = python38.pkgs.fetchPypi {
inherit pname version; inherit pname version;
sha256 = "43c2c9e5e7a16b6c88ba3088a9bfc82f7db8e13378be7c78d6c14a5f8ed05afd"; sha256 = "08fdd5ef7c96480ad11c12d472de21acd32359996f69a5259299b540feba4560";
}; };
doCheck = false; doCheck = false;
@ -290,12 +290,12 @@ with import <nixpkgs> {};
}; };
}; };
in python35.withPackages (ps: [ps.numpy my_toolz]) in python38.withPackages (ps: [ps.numpy my_toolz])
).env ).env
``` ```
Executing `nix-shell` will result in an environment in which you can use Executing `nix-shell` will result in an environment in which you can use
Python 3.5 and the `toolz` package. As you can see we had to explicitly mention Python 3.8 and the `toolz` package. As you can see we had to explicitly mention
for which Python version we want to build a package. for which Python version we want to build a package.
So, what did we do here? Well, we took the Nix expression that we used earlier So, what did we do here? Well, we took the Nix expression that we used earlier
@ -435,7 +435,7 @@ If we create a `shell.nix` file which calls `buildPythonPackage`, and if `src`
is a local source, and if the local source has a `setup.py`, then development is a local source, and if the local source has a `setup.py`, then development
mode is activated. mode is activated.
In the following example we create a simple environment that has a Python 3.5 In the following example we create a simple environment that has a Python 3.8
version of our package in it, as well as its dependencies and other packages we version of our package in it, as well as its dependencies and other packages we
like to have in the environment, all specified with `propagatedBuildInputs`. like to have in the environment, all specified with `propagatedBuildInputs`.
Indeed, we can just add any package we like to have in our environment to Indeed, we can just add any package we like to have in our environment to
@ -443,7 +443,7 @@ Indeed, we can just add any package we like to have in our environment to
```nix ```nix
with import <nixpkgs> {}; with import <nixpkgs> {};
with python35Packages; with python38Packages;
buildPythonPackage rec { buildPythonPackage rec {
name = "mypackage"; name = "mypackage";
@ -505,9 +505,9 @@ with import <nixpkgs> {};
( let ( let
toolz = callPackage /path/to/toolz/release.nix { toolz = callPackage /path/to/toolz/release.nix {
buildPythonPackage = python35Packages.buildPythonPackage; buildPythonPackage = python38Packages.buildPythonPackage;
}; };
in python35.withPackages (ps: [ ps.numpy toolz ]) in python38.withPackages (ps: [ ps.numpy toolz ])
).env ).env
``` ```
@ -515,8 +515,8 @@ Important to remember is that the Python version for which the package is made
depends on the `python` derivation that is passed to `buildPythonPackage`. Nix depends on the `python` derivation that is passed to `buildPythonPackage`. Nix
tries to automatically pass arguments when possible, which is why generally you tries to automatically pass arguments when possible, which is why generally you
don't explicitly define which `python` derivation should be used. In the above don't explicitly define which `python` derivation should be used. In the above
example we use `buildPythonPackage` that is part of the set `python35Packages`, example we use `buildPythonPackage` that is part of the set `python38Packages`,
and in this case the `python35` interpreter is automatically used. and in this case the `python38` interpreter is automatically used.
## Reference ## Reference
@ -662,7 +662,7 @@ following are specific to `buildPythonPackage`:
variables which will be available when the binary is run. For example, variables which will be available when the binary is run. For example,
`makeWrapperArgs = ["--set FOO BAR" "--set BAZ QUX"]`. `makeWrapperArgs = ["--set FOO BAR" "--set BAZ QUX"]`.
* `namePrefix`: Prepends text to `${name}` parameter. In case of libraries, this * `namePrefix`: Prepends text to `${name}` parameter. In case of libraries, this
defaults to `"python3.5-"` for Python 3.5, etc., and in case of applications defaults to `"python3.8-"` for Python 3.8, etc., and in case of applications
to `""`. to `""`.
* `pythonPath ? []`: List of packages to be added into `$PYTHONPATH`. Packages * `pythonPath ? []`: List of packages to be added into `$PYTHONPATH`. Packages
in `pythonPath` are not propagated (contrary to `propagatedBuildInputs`). in `pythonPath` are not propagated (contrary to `propagatedBuildInputs`).
@ -960,7 +960,7 @@ has security implications and is relevant for those using Python in a
When the environment variable `DETERMINISTIC_BUILD` is set, all bytecode will When the environment variable `DETERMINISTIC_BUILD` is set, all bytecode will
have timestamp 1. The `buildPythonPackage` function sets `DETERMINISTIC_BUILD=1` have timestamp 1. The `buildPythonPackage` function sets `DETERMINISTIC_BUILD=1`
and [PYTHONHASHSEED=0](https://docs.python.org/3.5/using/cmdline.html#envvar-PYTHONHASHSEED). and [PYTHONHASHSEED=0](https://docs.python.org/3.8/using/cmdline.html#envvar-PYTHONHASHSEED).
Both are also exported in `nix-shell`. Both are also exported in `nix-shell`.
@ -1014,7 +1014,7 @@ with import <nixpkgs> {};
packageOverrides = self: super: { packageOverrides = self: super: {
pandas = super.pandas.overridePythonAttrs(old: {name="foo";}); pandas = super.pandas.overridePythonAttrs(old: {name="foo";});
}; };
in pkgs.python35.override {inherit packageOverrides;}; in pkgs.python38.override {inherit packageOverrides;};
in python.withPackages(ps: [ps.pandas])).env in python.withPackages(ps: [ps.pandas])).env
``` ```
@ -1036,7 +1036,7 @@ with import <nixpkgs> {};
packageOverrides = self: super: { packageOverrides = self: super: {
scipy = super.scipy_0_17; scipy = super.scipy_0_17;
}; };
in (pkgs.python35.override {inherit packageOverrides;}).withPackages (ps: [ps.blaze]) in (pkgs.python38.override {inherit packageOverrides;}).withPackages (ps: [ps.blaze])
).env ).env
``` ```