02: Python Packages for Pyramid Applications¶
Most modern Python development is done using Python packages, an approach Pyramid puts to good use. In this step we redo "Hello World" as a minimum Python package inside a minimum Python project.
Background¶
Python developers can organize a collection of modules and files into a
namespaced unit called a package. If a
directory is on sys.path
and has a special file named
__init__.py
, it is treated as a Python package.
Packages can be bundled up, made available for installation,
and installed through a (muddled, but improving) toolchain oriented
around a setup.py
file for a
setuptools project.
Explaining it all in this
tutorial will induce madness. For this tutorial, this is all you need to
know:
- We will have a directory for each tutorial step as a setuptools project
- This project will contain a
setup.py
which injects the features of the setuptool's project machinery into the directory - In this project we will make a
tutorial
subdirectory into a Python package using an__init__.py
Python module file - We will run
python setup.py develop
to install our project in development mode
In summary:
- You'll do your development in a Python package
- That package will be part of a setuptools project
Objectives¶
- Make a Python "package" directory with an
__init__.py
- Get a minimum Python "project" in place by making a
setup.py
- Install our
tutorial
project in development mode
Steps¶
Make an area for this tutorial step:
$ cd ..; mkdir package; cd package
In
package/setup.py
, enter the following:from setuptools import setup requires = [ 'pyramid', ] setup(name='tutorial', install_requires=requires, )
Make the new project installed for development then make a directory for the actual code:
$ $VENV/bin/python setup.py develop $ mkdir tutorial
Enter the following into
package/tutorial/__init__.py
:# package
Enter the following into
package/tutorial/app.py
:from wsgiref.simple_server import make_server from pyramid.config import Configurator from pyramid.response import Response def hello_world(request): print ('Incoming request') return Response('<body><h1>Hello World!</h1></body>') if __name__ == '__main__': config = Configurator() config.add_route('hello', '/') config.add_view(hello_world, route_name='hello') app = config.make_wsgi_app() server = make_server('0.0.0.0', 6543, app) server.serve_forever()
Run the WSGI application with:
$ $VENV/bin/python tutorial/app.py
Open http://localhost:6543/ in your browser.
Analysis¶
Python packages give us an organized unit of project development.
Python projects, via setup.py
, gives us special features when
our package is installed (in this case, in local development mode.)
In this step we have a Python package called tutorial
. We use the
same name in each step of the tutorial, to avoid unnecessary retyping.
Above this tutorial
directory we have the files that handle the
packaging of this project. At the moment, all we need is a
bare-bones setup.py
.
Everything else is the same about our application. We simply made a
Python package with a setup.py
and installed it in development mode.
Note that the way we're running the app (python tutorial/app.py
) is a bit
of an odd duck. We would never do this unless we were writing a tutorial that
tries to capture how this stuff works a step at a time. It's generally a bad
idea to run a Python module inside a package directly as a script.
See also