mirror of
https://github.com/NixOS/nix.dev.git
synced 2024-10-18 14:32:43 -04:00
95 lines
2.5 KiB
Markdown
95 lines
2.5 KiB
Markdown
# Set up a development environment
|
|
|
|
Let's build a Python web application using the Flask web framework as an exercise.
|
|
|
|
Create a new file called `default.nix`. This file is conventionally used for specifying packages. Add the code:
|
|
|
|
|
|
|
|
```{code-block} nix default.nix
|
|
{ pkgs ? import <nixpkgs> {} }:
|
|
|
|
pkgs.python3Packages.buildPythonApplication {
|
|
pname = "myapp";
|
|
src = ./.;
|
|
version = "0.1";
|
|
propagatedBuildInputs = [ pkgs.python3Packages.flask ];
|
|
}
|
|
```
|
|
|
|
You will also need a simple Flask app as `myapp.py`:
|
|
|
|
```{code-block} python myapp.py
|
|
#! /usr/bin/env python
|
|
|
|
from flask import Flask
|
|
|
|
app = Flask(__name__)
|
|
|
|
@app.route("/")
|
|
def hello():
|
|
return "Hello, Nix!"
|
|
|
|
def run():
|
|
app.run(host="0.0.0.0")
|
|
|
|
if __name__ == "__main__":
|
|
run()
|
|
```
|
|
|
|
And a `setup.py` script:
|
|
|
|
```{code-block} python setup.py
|
|
from setuptools import setup
|
|
|
|
setup(
|
|
name='myapp',
|
|
version='0.1',
|
|
py_modules=['myapp'],
|
|
entry_points={
|
|
'console_scripts': ['myapp = myapp:run']
|
|
},
|
|
)
|
|
```
|
|
|
|
Now build the package with:
|
|
|
|
```{code-block} bash test_nix_build.sh
|
|
nix-build
|
|
```
|
|
|
|
This will create a symbolic link `result` to our package's path in the Nix store, which looks like `/nix/store/6i4l781jwk5vbia8as32637207kgkllj-myapp-0.1`. Look around to see what's inside.
|
|
|
|
You may notice we can run the application from the package like this: `./result/bin/myapp`. But we can also use the `default.nix` as a shell environment to get the same result:
|
|
|
|
```bash
|
|
nix-shell default.nix
|
|
python myapp.py
|
|
```
|
|
|
|
In this context, Nix takes on the role that you would otherwise use pip or virtualenv for. Nix installs required dependencies and separates the environment from others on your system.
|
|
|
|
You can check this Nix configuration into version control and share it with others to make sure you are all running the same software. This is a great way to prevent configuration drift between different team members & contributors, especially when a project has many dependencies.
|
|
|
|
You can also run a bash script like this one in your CI to make sure your `default.nix` keeps working in the future.
|
|
|
|
```{code-block} bash test_myapp.sh
|
|
#!/usr/bin/env nix-shell
|
|
#! nix-shell -i bash
|
|
set -euo pipefail
|
|
|
|
# start myapp in background and save the process id
|
|
python myapp.py >> /dev/null 2>&1 &
|
|
pid=$!
|
|
|
|
if [[ $(curl --retry 3 --retry-delay 1 --retry-connrefused http://127.0.0.1:5000) == "Hello, Nix!" ]]; then
|
|
echo "SUCCESS: myapp.py is serving the expected string"
|
|
kill $pid
|
|
exit 0
|
|
else
|
|
echo "FAIL: myapp.py is not serving the expected string"
|
|
kill $pid
|
|
exit 1
|
|
fi
|
|
```
|