Use Pyramid's pserve
command with a .ini
configuration file for simpler, better application running.
Pyramid has a first-class concept of configuration <configuration_narr>
distinct from code. This approach is optional, but its presence makes it distinct from other Python web frameworks. It taps into Python's setuptools
library, which establishes conventions for installing and providing "entry points" for Python projects. Pyramid uses an entry point to let a Pyramid application know where to find the WSGI app.
- Modify our
setup.py
to have an entry point telling Pyramid the location of the WSGI app. - Create an application driven by an
.ini
file. - Start the application with Pyramid's
pserve
command. - Move code into the package's
__init__.py
.
First we copy the results of the previous step:
$ cd ..; cp -r package ini; cd ini
Our
ini/setup.py
needs a setuptools "entry point" in thesetup()
function:ini/setup.py
We can now install our project, thus generating (or re-generating) an "egg" at
ini/tutorial.egg-info
:$ $VENV/bin/pip install -e .
Let's make a file
ini/development.ini
for our configuration:ini/development.ini
We can refactor our startup code from the previous step's
app.py
intoini/tutorial/__init__.py
:ini/tutorial/__init__.py
Now that
ini/tutorial/app.py
isn't used, let's remove it:$ rm tutorial/app.py
Run your Pyramid application with:
$ $VENV/bin/pserve development.ini --reload
- Open http://localhost:6543/.
Our development.ini
file is read by pserve
and serves to bootstrap our application. Processing then proceeds as described in the Pyramid chapter on application startup <startup_chapter>
:
pserve
looks for[app:main]
and findsuse = egg:tutorial
.- The projects's
setup.py
has defined an "entry point" (lines 10-13) for the project's "main" entry point oftutorial:main
. - The
tutorial
package's__init__
has amain
function. - This function is invoked, with the values from certain
.ini
sections passed in.
The .ini
file is also used for two other functions:
Configuring the WSGI server.
[server:main]
wires up the choice of which WSGI server for your WSGI application. In this case, we are usingwaitress
which we specified intutorial/setup.py
and was installed in therequirements
step at the start of this tutorial. It also wires up the port number:listen = localhost:6543
tellswaitress
to listen on hostlocalhost
at port6543
.Note
Running the command
$VENV/bin/pip install -e .
will check for previously installed packages in our virtual environment that are specified in our package'ssetup.py
file, then install our package in editable mode, installing any requirements that were not previously installed. If a requirement was manually installed previously on the command line or otherwise, in this case Waitress, then$VENV/bin/pip install -e .
will merely check that it is installed and move on.- Configuring Python logging. Pyramid uses Python standard logging, which needs a number of configuration values. The
.ini
serves this function. This provides the console log output that you see on startup and each request.
We moved our startup code from app.py
to the package's tutorial/__init__.py
. This isn't necessary, but it is a common style in Pyramid to take the WSGI app bootstrapping out of your module's code and put it in the package's __init__.py
.
The pserve
application runner has a number of command-line arguments and options. We are using --reload
which tells pserve
to watch the filesystem for changes to relevant code (Python files, the INI file, etc.) and, when something changes, restart the application. Very handy during development.
- If you don't like configuration and/or
.ini
files, could you do this yourself in Python code? - Can we have multiple
.ini
configuration files for a project? Why might you want to do that? - The entry point in
setup.py
didn't mention__init__.py
when it declaredtutorial:main
function. Why not? - What is the purpose of
**settings
? What does the**
signify?
project_narr
, cookiecutters
, what_is_this_pserve_thing
, environment_chapter
, paste_chapter