============================================ 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 minimal Python package inside a minimal Python project. Background ========== Python developers can organize a collection of modules and files into a namespaced unit called a :ref:`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 toolchain oriented around a ``setup.py`` file. For this tutorial, this is all you need to know: - We will have a directory for each tutorial step as a *project*. - This project will contain a ``setup.py`` which injects the features of the 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 ``pip install -e .`` 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 *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: .. code-block:: bash cd ..; mkdir package; cd package #. In ``package/setup.py``, enter the following: .. literalinclude:: package/setup.py #. Make the new project installed for development then make a directory for the actual code: .. code-block:: bash $VENV/bin/pip install -e . mkdir tutorial #. Enter the following into ``package/tutorial/__init__.py``: .. literalinclude:: package/tutorial/__init__.py #. Enter the following into ``package/tutorial/app.py``: .. literalinclude:: package/tutorial/app.py #. Run the WSGI application with: .. code-block:: bash $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``, give us special features when our package is installed (in this case, in local development mode, also called local editable mode as indicated by ``-e .``). 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 one step at a time. It's generally a bad idea to run a Python module inside a package directly as a script. .. seealso:: :ref:`Python Packages ` and `Working in "Development Mode" `_.