As we saw in firstapp_chapter
, it's possible to create a Pyramid
application completely manually. However, it's usually more convenient to use a scaffold
to generate a basic Pyramid
project
.
A project is a directory that contains at least one Python package
. You'll use a scaffold to create a project, and you'll create your application logic within a package that lives inside the project. Even if your application is extremely simple, it is useful to place code that drives the application within a package, because (1) a package is more easily extended with new code, and (2) an application that lives inside a package can also be distributed more easily than one which does not live within a package.
Pyramid
comes with a variety of scaffolds that you can use to generate a project. Each scaffold makes different configuration assumptions about what type of application you're trying to construct.
These scaffolds are rendered using the pcreate
command that is installed as part of Pyramid.
single: scaffolds single: starter scaffold single: zodb scaffold single: alchemy scaffold
The convenience scaffolds included with Pyramid
differ from each other on a number of axes:
- the persistence mechanism they offer (no persistence mechanism,
ZODB
, orSQLAlchemy
) - the mechanism they use to map URLs to code (
traversal
orURL dispatch
)
The included scaffolds are these:
starter
URL mapping via
URL dispatch
and no persistence mechanismzodb
URL mapping via
traversal
and persistence viaZODB
alchemy
URL mapping via
URL dispatch
and persistence viaSQLAlchemy
single: creating a project single: project single: pcreate
See also the output of pcreate --help <pcreate_script>
.
In installing_chapter
, you created a virtual Python environment via the venv
command. To start a Pyramid
project
, use the pcreate
command installed within the virtual environment. We'll choose the starter
scaffold for this purpose. When we invoke pcreate
, it will create a directory that represents our project.
In installing_chapter
we called the virtual environment directory env
. The following commands assume that our current working directory is the env
directory.
The below example uses the pcreate
command to create a project with the starter
scaffold.
On UNIX:
$ $VENV/bin/pcreate -s starter MyProject
Or on Windows:
c:\> %VENV%\Scripts\pcreate -s starter MyProject
As a result of invoking the pcreate
command, a directory named MyProject
is created. That directory is a project
directory. The setup.py
file in that directory can be used to distribute your application, or install your application for deployment or development.
An .ini
file named development.ini
will be created in the project directory. You will use this .ini
file to configure a server, to run your application, and to debug your application. It contains configuration that enables an interactive debugger and settings optimized for development.
Another .ini
file named production.ini
will also be created in the project directory. It contains configuration that disables any interactive debugger (to prevent inappropriate access and disclosure), and turns off a number of debugging settings. You can use this file to put your application into production.
The MyProject
project directory contains an additional subdirectory named myproject
(note the case difference) representing a Python package
which holds very simple Pyramid
sample code. This is where you'll edit your application's Python code and templates.
We created this project within an env
virtual environment directory. However, note that this is not mandatory. The project directory can go more or less anywhere on your filesystem. You don't need to put it in a special "web server" directory, and you don't need to put it within a virtual environment directory. The author uses Linux mainly, and tends to put project directories which he creates within his ~/projects
directory. On Windows, it's a good idea to put project directories within a directory that contains no space characters, so it's wise to avoid a path that contains, i.e., My Documents
. As a result, the author, when he uses Windows, just puts his projects in C:\projects
.
Warning
You'll need to avoid using pcreate
to create a project with the same name as a Python standard library component. In particular, this means you should avoid using the names site
or test
, both of which conflict with Python standard library packages. You should also avoid using the name pyramid
, which will conflict with Pyramid itself.
single: setup.py develop single: development install
To install a newly created project for development, you should cd
to the newly created project directory and use the Python interpreter from the virtual environment
you created during installing_chapter
to invoke the command pip install -e .
, which installs the project in development mode (-e
is for "editable") into the current directory (.
).
The file named setup.py
will be in the root of the pcreate-generated project directory. The python
you're invoking should be the one that lives in the bin
(or Scripts
on Windows) directory of your virtual Python environment. Your terminal's current working directory must be the newly created project directory.
On UNIX:
$ cd MyProject
$ $VENV/bin/pip install -e .
Or on Windows:
c:\> cd MyProject
c:\> %VENV%\Scripts\pip install -e .
Elided output from a run of this command on UNIX is shown below:
$ cd MyProject
$ $VENV/bin/pip install -e .
...
Successfully installed Chameleon-2.24 Mako-1.0.4 MyProject \
pyramid-chameleon-0.3 pyramid-debugtoolbar-2.4.2 pyramid-mako-1.0.2
This will install a distribution
representing your project into the virtual environment interpreter's library set so it can be found by import
statements and by other console scripts such as pserve
, pshell
, proutes
, and pviews
.
single: running tests single: tests (running)
To run unit tests for your application, you must first install the testing dependencies.
On UNIX:
$ $VENV/bin/pip install -e ".[testing]"
On Windows:
c:\> %VENV%\Scripts\pip install -e ".[testing]"
Once the testing requirements are installed, then you can run the tests using the py.test
command that was just installed in the bin
directory of your virtual environment.
On UNIX:
$ $VENV/bin/py.test -q
On Windows:
c:\> %VENV%\Scripts\py.test -q
Here's sample output from a test run on UNIX:
$ $VENV/bin/py.test -q
..
2 passed in 0.47 seconds
The tests themselves are found in the tests.py
module in your pcreate
generated project. Within a project generated by the starter
scaffold, only two sample tests exist.
Note
The -q
option is passed to the py.test
command to limit the output to a stream of dots. If you don't pass -q
, you'll see verbose test result output (which normally isn't very useful).
Alternatively, if you'd like to see test coverage, pass the --cov
option to py.test
:
$ $VENV/bin/py.test --cov -q
Scaffolds include configuration defaults for py.test
and test coverage. These configuration files are pytest.ini
and .coveragerc
, located at the root of your package. Without these defaults, we would need to specify the path to the module on which we want to run tests and coverage.
$ $VENV/bin/py.test --cov=myproject myproject/tests.py -q
See py.test's documentation for pytest:usage
or invoke py.test -h
to see its full set of options.
single: running an application single: pserve single: reload single: startup
See also the output of pserve --help <pserve_script>
.
Once a project is installed for development, you can run the application it represents using the pserve
command against the generated configuration file. In our case, this file is named development.ini
.
On UNIX:
$ $VENV/bin/pserve development.ini
On Windows:
c:\> %VENV%\Scripts\pserve development.ini
Here's sample output from a run of pserve
on UNIX:
$ $VENV/bin/pserve development.ini
Starting server in PID 16208.
serving on http://127.0.0.1:6543
Access is restricted such that only a browser running on the same machine as Pyramid will be able to access your Pyramid application. However, if you want to open access to other machines on the same network, then edit the development.ini
file, and replace the host
value in the [server:main]
section, changing it from 127.0.0.1
to 0.0.0.0
. For example:
[server:main]
use = egg:waitress#main
host = 0.0.0.0
port = 6543
Now when you use pserve
to start the application, it will respond to requests on all IP addresses possessed by your system, not just requests to localhost
. This is what the 0.0.0.0
in serving on http://0.0.0.0:6543
means. The server will respond to requests made to 127.0.0.1
and on any external IP address. For example, your system might be configured to have an external IP address 192.168.1.50
. If that's the case, if you use a browser running on the same system as Pyramid, it will be able to access the application via http://127.0.0.1:6543/
as well as via http://192.168.1.50:6543/
. However, other people on other computers on the same network will also be able to visit your Pyramid application in their browser by visiting http://192.168.1.50:6543/
.
You can change the port on which the server runs on by changing the same portion of the development.ini
file. For example, you can change the port = 6543
line in the development.ini
file's [server:main]
section to port = 8080
to run the server on port 8080 instead of port 6543.
You can shut down a server started this way by pressing Ctrl-C
(or Ctrl-Break
on Windows).
The default server used to run your Pyramid application when a project is created from a scaffold is named Waitress
. This server is what prints the serving on...
line when you run pserve
. It's a good idea to use this server during development because it's very simple. It can also be used for light production. Setting your application up under a different server is not advised until you've done some development work under the default server, particularly if you're not yet experienced with Python web development. Python web server setup can be complex, and you should get some confidence that your application works in a default environment before trying to optimize it or make it "more like production". It's awfully easy to get sidetracked trying to set up a non-default server for hours without actually starting to do any development. One of the nice things about Python web servers is that they're largely interchangeable, so if your application works under the default server, it will almost certainly work under any other server in production if you eventually choose to use a different one. Don't worry about it right now.
For more detailed information about the startup process, see startup_chapter
. For more information about environment variables and configuration file settings that influence startup and runtime behavior, see environment_chapter
.
During development, it's often useful to run pserve
using its --reload
option. When --reload
is passed to pserve
, changes to any Python module your project uses will cause the server to restart. This typically makes development easier, as changes to Python code made within a Pyramid
application is not put into effect until the server restarts.
For example, on UNIX:
$ $VENV/bin/pserve development.ini --reload
Starting subprocess with file monitor
Starting server in PID 16601.
serving on http://127.0.0.1:6543
Now if you make a change to any of your project's .py
files or .ini
files, you'll see the server restart automatically:
development.ini changed; reloading...
-------------------- Restarting --------------------
Starting server in PID 16602.
serving on http://127.0.0.1:6543
Changes to template files (such as .pt
or .mak
files) won't cause the server to restart. Changes to template files don't require a server restart as long as the pyramid.reload_templates
setting in the development.ini
file is true
. Changes made to template files when this setting is true will take effect immediately without a server restart.
single: WSGI
Once your application is running via pserve
, you may visit http://localhost:6543/
in your browser. You will see something in your browser like what is displayed in the following image:
This is the page shown by default when you visit an unmodified pcreate
generated starter
application in a browser.
single: debug toolbar
If you click on the Pyramid
logo at the top right of the page, a new target window will open to present a debug toolbar that provides various niceties while you're developing. This logo will float above every HTML page served by Pyramid
while you develop an application, and allows you to show the toolbar as necessary.
If you don't see the Pyramid logo on the top right of the page, it means you're browsing from a system that does not have debugging access. By default, for security reasons, only a browser originating from localhost
(127.0.0.1
) can see the debug toolbar. To allow your browser on a remote system to access the server, add a line within the [app:main]
section of the development.ini
file in the form debugtoolbar.hosts = X .X.X.X
. For example, if your Pyramid application is running on a remote system, and you're browsing from a host with the IP address 192.168.1.1
, you'd add something like this to enable the toolbar when your system contacts Pyramid:
[app:main]
# .. other settings ...
debugtoolbar.hosts = 192.168.1.1
For more information about what the debug toolbar allows you to do, see the documentation for pyramid_debugtoolbar <toolbar:overview>
.
The debug toolbar will not be shown (and all debugging will be turned off) when you use the production.ini
file instead of the development.ini
ini file to run the application.
You can also turn the debug toolbar off by editing development.ini
and commenting out a line. For example, instead of:
[app:main]
# ... elided configuration
pyramid.includes =
pyramid_debugtoolbar
Put a hash mark at the beginning of the pyramid_debugtoolbar
line:
[app:main]
# ... elided configuration
pyramid.includes =
# pyramid_debugtoolbar
Then restart the application to see that the toolbar has been turned off.
Note that if you comment out the pyramid_debugtoolbar
line, the #
must be in the first column. If you put it anywhere else, and then attempt to restart the application, you'll receive an error that ends something like this:
ImportError: No module named #pyramid_debugtoolbar
single: project structure
The starter
scaffold generated a project
(named MyProject
), which contains a Python package
. The package is also named myproject
, but it's lowercased; the scaffold generates a project which contains a package that shares its name except for case.
All Pyramid
pcreate
-generated projects share a similar structure. The MyProject
project we've generated has the following directory structure:
MyProject/
|-- CHANGES.txt
|-- development.ini
|-- MANIFEST.in
|-- myproject
| |-- __init__.py
| |-- static
| | |-- pyramid-16x16.png
| | |-- pyramid.png
| | |-- theme.css
| | `-- theme.min.css
| |-- templates
| | `-- mytemplate.pt
| |-- tests.py
| `-- views.py
|-- production.ini
|-- README.txt
`-- setup.py
The MyProject
project
directory is the distribution and deployment wrapper for your application. It contains both the myproject
package
representing your application as well as files used to describe, run, and test your application.
CHANGES.txt
describes the changes you've made to the application. It is conventionally written inReStructuredText
format.README.txt
describes the application in general. It is conventionally written inReStructuredText
format.development.ini
is aPasteDeploy
configuration file that can be used to execute your application during development.production.ini
is aPasteDeploy
configuration file that can be used to execute your application in a production configuration.MANIFEST.in
is adistutils
"manifest" file, naming which files should be included in a source distribution of the package whenpython setup.py sdist
is run.setup.py
is the file you'll use to test and distribute your application. It is a standardsetuptools
setup.py
file.
single: PasteDeploy single: ini file
The development.ini
file is a PasteDeploy
configuration file. Its purpose is to specify an application to run when you invoke pserve
, as well as the deployment settings provided to that application.
The generated development.ini
file looks like so:
MyProject/development.ini
This file contains several sections including [app:main]
, [server:main]
, and several other sections related to logging configuration.
The [app:main]
section represents configuration for your Pyramid
application. The use
setting is the only setting required to be present in the [app:main]
section. Its default value, egg:MyProject
, indicates that our MyProject project contains the application that should be served. Other settings added to this section are passed as keyword arguments to the function named main
in our package's __init__.py
module. You can provide startup-time configuration parameters to your application by adding more settings to this section.
See pastedeploy_entry_points
for more information about the meaning of the use = egg:MyProject
value in this section.
The pyramid.reload_templates
setting in the [app:main]
section is a Pyramid
-specific setting which is passed into the framework. If it exists, and its value is true
, supported template changes will not require an application restart to be detected. See reload_templates_section
for more information.
Warning
The pyramid.reload_templates
option should be turned off for production applications, as template rendering is slowed when it is turned on.
The pyramid.includes
setting in the [app:main]
section tells Pyramid to "include" configuration from another package. In this case, the line pyramid.includes = pyramid_debugtoolbar
tells Pyramid to include configuration from the pyramid_debugtoolbar
package. This turns on a debugging panel in development mode which can be opened by clicking on the Pyramid
logo on the top right of the screen. Including the debug toolbar will also make it possible to interactively debug exceptions when an error occurs.
Various other settings may exist in this section having to do with debugging or influencing runtime behavior of a Pyramid
application. See environment_chapter
for more information about these settings.
The name main
in [app:main]
signifies that this is the default application run by pserve
when it is invoked against this configuration file. The name main
is a convention used by PasteDeploy signifying that it is the default application.
The [server:main]
section of the configuration file configures a WSGI server which listens on TCP port 6543. It is configured to listen on localhost only (127.0.0.1
).
The sections after # logging configuration
represent Python's standard library logging
module configuration for your application. These sections are passed to the logging module's config file configuration engine when the pserve
or pshell
commands are executed. The default configuration sends application logging output to the standard error output of your terminal. For more information about logging configuration, see logging_chapter
.
See the PasteDeploy
documentation for more information about other types of things you can put into this .ini
file, such as other applications, middleware
, and alternate WSGI
server implementations.
single: production.ini
The production.ini
file is a PasteDeploy
configuration file with a purpose much like that of development.ini
. However, it disables the debug toolbar, and filters all log messages except those above the WARN level. It also turns off template development options such that templates are not automatically reloaded when changed, and turns off all debugging options. This file is appropriate to use instead of development.ini
when you put your application into production.
It's important to use production.ini
(and not development.ini
) to benchmark your application and put it into production. development.ini
configures your system with a debug toolbar that helps development, but the inclusion of this toolbar slows down page rendering times by over an order of magnitude. The debug toolbar is also a potential security risk if you have it configured incorrectly.
single: MANIFEST.in
The MANIFEST.in
file is a distutils
configuration file which specifies the non-Python files that should be included when a distribution
of your Pyramid project is created when you run python setup.py sdist
. Due to the information contained in the default MANIFEST.in
, an sdist of your Pyramid project will include .txt
files, .ini
files, .rst
files, graphics files, and template files, as well as .py
files. See https://docs.python.org/2/distutils/sourcedist.html#the-manifest-in-template for more information about the syntax and usage of MANIFEST.in
.
Without the presence of a MANIFEST.in
file or without checking your source code into a version control repository, setup.py sdist
places only Python source files (files ending with a .py
extension) into tarballs generated by python setup.py sdist
. This means, for example, if your project was not checked into a setuptools-compatible source control system, and your project directory didn't contain a MANIFEST.in
file that told the sdist
machinery to include *.pt
files, the myproject/templates/mytemplate.pt
file would not be included in the generated tarball.
Projects generated by Pyramid scaffolds include a default MANIFEST.in
file. The MANIFEST.in
file contains declarations which tell it to include files like *.pt
, *.css
and *.js
in the generated tarball. If you include files with extensions other than the files named in the project's MANIFEST.in
and you don't make use of a setuptools-compatible version control system, you'll need to edit the MANIFEST.in
file and include the statements necessary to include your new files. See https://docs.python.org/2/distutils/sourcedist.html#principle for more information about how to do this.
You can also delete MANIFEST.in
from your project and rely on a setuptools feature which simply causes all files checked into a version control system to be put into the generated tarball. To allow this to happen, check all the files that you'd like to be distributed along with your application's Python files into Subversion. After you do this, when you rerun setup.py sdist
, all files checked into the version control system will be included in the tarball. If you don't use Subversion, and instead use a different version control system, you may need to install a setuptools add-on such as setuptools-git
or setuptools-hg
for this behavior to work properly.
single: setup.py
The setup.py
file is a setuptools
setup file. It is meant to be used to define requirements for installing dependencies for your package and testing, as well as distributing your application.
Note
setup.py
is the de facto standard which Python developers use to distribute their reusable code. You can read more about setup.py
files and their usage in the Python Packaging User Guide and Setuptools documentation.
Our generated setup.py
looks like this:
MyProject/setup.py
The setup.py
file calls the setuptools setup
function, which does various things depending on the arguments passed to pip
on the command line.
Within the arguments to this function call, information about your application is kept. While it's beyond the scope of this documentation to explain everything about setuptools setup files, we'll provide a whirlwind tour of what exists in this file in this section.
Your application's name can be any string; it is specified in the name
field. The version number is specified in the version
value. A short description is provided in the description
field. The long_description
is conventionally the content of the README
and CHANGES
files appended together. The classifiers
field is a list of Trove classifiers describing your application. author
and author_email
are text fields which probably don't need any description. url
is a field that should point at your application project's URL (if any). packages=find_packages()
causes all packages within the project to be found when packaging the application. include_package_data
will include non-Python files when the application is packaged if those files are checked into version control. zip_safe=False
indicates that this package is not safe to use as a zipped egg; instead it will always unpack as a directory, which is more convenient. install_requires
indicates that this package depends on the pyramid
package. extras_require
is a Python dictionary that defines what is required to be installed for running tests. We examined entry_points
in our discussion of the development.ini
file; this file defines the main
entry point that represents our project's application.
Usually you only need to think about the contents of the setup.py
file when distributing your application to other people, when adding Python package dependencies, or when versioning your application for your own use. For fun, you can try this command now:
$ $VENV/bin/python setup.py sdist
This will create a tarball of your application in a dist
subdirectory named MyProject-0.0.tar.gz
. You can send this tarball to other people who want to install and use your application.
single: package
The myproject
package
lives inside the MyProject
project
. It contains:
- An
__init__.py
file signifies that this is a Pythonpackage
. It also contains code that helps users run the application, including amain
function which is used as a entry point for commands such aspserve
,pshell
,pviews
, and others. - A
templates
directory, which containsChameleon
(or other types of) templates. - A
tests.py
module, which contains unit test code for the application. - A
views.py
module, which contains view code for the application.
These are purely conventions established by the scaffold. Pyramid
doesn't insist that you name things in any particular way. However, it's generally a good idea to follow Pyramid standards for naming, so that other Pyramid developers can get up to speed quickly on your code when you need help.
single: __init.py
We need a small Python module that configures our application and which advertises an entry point for use by our PasteDeploy
.ini
file. This is the file named __init__.py
. The presence of an __init__.py
also informs Python that the directory which contains it is a package.
MyProject/myproject/__init__.py
- Line 1 imports the
Configurator
class frompyramid.config
that we use later. Lines 4-12 define a function named
main
that returns aPyramid
WSGI application. This function is meant to be called by thePasteDeploy
framework as a result of runningpserve
.Within this function, application configuration is performed.
Line 7 creates an instance of a
Configurator
.Line 8 adds support for Chameleon templating bindings, allowing us to specify renderers with the
.pt
extension.Line 9 registers a static view, which will serve up the files from the
myproject:static
asset specification
(thestatic
directory of themyproject
package).Line 10 adds a
route
to the configuration. This route is later used by a view in theviews
module.Line 11 calls
config.scan()
, which picks up view registrations declared elsewhere in the package (in this case, in theviews.py
module).Line 12 returns a
WSGI
application to the caller of the function (Pyramid's pserve).
single: views.py
Much of the heavy lifting in a Pyramid
application is done by view callables. A view callable
is the main tool of a Pyramid
web application developer; it is a bit of code which accepts a request
and which returns a response
.
MyProject/myproject/views.py
Lines 4-6 define and register a view callable
named my_view
. The function named my_view
is decorated with a view_config
decorator (which is processed by the config.scan()
line in our __init__.py
). The view_config decorator asserts that this view be found when a route
named home
is matched. In our case, because our __init__.py
maps the route named home
to the URL pattern /
, this route will match when a visitor visits the root URL. The view_config decorator also names a renderer
, which in this case is a template that will be used to render the result of the view callable. This particular view declaration points at templates/mytemplate.pt
, which is an asset specification
that specifies the mytemplate.pt
file within the templates
directory of the myproject
package. The asset specification could have also been specified as myproject:templates/mytemplate.pt
; the leading package name and colon is optional. The template file pointed to is a Chameleon
ZPT template file (templates/my_template.pt
).
This view callable function is handed a single piece of information: the request
. The request is an instance of the WebOb
Request
class representing the browser's request to our server.
This view is configured to invoke a renderer
on a template. The dictionary the view returns (on line 6) provides the value the renderer substitutes into the template when generating HTML. The renderer then returns the HTML in a response
.
Note
Dictionaries provide values to template
s.
Note
When the application is run with the scaffold's default
development.ini <MyProject_ini>
configuration, logging is set up
<MyProject_ini_logging>
to aid debugging. If an exception is raised, uncaught tracebacks are displayed after the startup messages on the
console running the server <running_the_project_application>
. Also print()
statements may be inserted into the application for debugging to send output to this console.
Note
development.ini
has a setting that controls how templates are reloaded, pyramid.reload_templates
.
- When set to
True
(as in the scaffolddevelopment.ini
), changed templates automatically reload without a server restart. This is convenient while developing, but slows template rendering speed. - When set to
False
(the default value), changing templates requires a server restart to reload them. Production applications should usepyramid.reload_templates = False
.
See also views_which_use_a_renderer
for more information about how views, renderers, and templates relate and cooperate.
Pyramid can also dynamically reload changed Python files. See also reloading_code
.
See also the debug_toolbar
, which provides interactive access to your application's internals and, should an exception occur, allows interactive access to traceback execution stack frames from the Python interpreter.
single: static directory
This directory contains static assets which support the mytemplate.pt
template. It includes CSS and images.
This is the single Chameleon
template that exists in the project. Its contents are too long to show here, but it displays a default page when rendered. It is referenced by the call to @view_config
as the renderer
of the my_view
view callable in the views.py
file. See views_which_use_a_renderer
for more information about renderers.
Templates are accessed and used by view configurations and sometimes by view functions themselves. See templates_used_directly
and templates_used_as_renderers
.
single: tests.py
The tests.py
module includes unit tests for your application.
MyProject/myproject/tests.py
This sample tests.py
file has one unit test and one functional test defined within it. These tests are executed when you run py.test -q
. You may add more tests here as you build your application. You are not required to write tests to use Pyramid
. This file is simply provided for convenience and example.
See testing_chapter
for more information about writing Pyramid
unit tests.
pair: modifying; package structure
It is best practice for your application's code layout to not stray too much from accepted Pyramid scaffold defaults. If you refrain from changing things very much, other Pyramid coders will be able to more quickly understand your application. However, the code layout choices made for you by a scaffold are in no way magical or required. Despite the choices made for you by any scaffold, you can decide to lay your code out any way you see fit.
For example, the configuration method named ~pyramid.config.Configurator.add_view
requires you to pass a dotted Python name
or a direct object reference as the class or function to be used as a view. By default, the starter
scaffold would have you add view functions to the views.py
module in your package. However, you might be more comfortable creating a views
directory, and adding a single file for each view.
If your project package name was myproject
and you wanted to arrange all your views in a Python subpackage within the myproject
package
named views
instead of within a single views.py
file, you might do the following.
- Create a
views
directory inside yourmyproject
package directory (the same directory which holdsviews.py
). - Create a file within the new
views
directory named__init__.py
. (It can be empty. This just tells Python that theviews
directory is a package.) - Move the content from the existing
views.py
file to a file inside the newviews
directory named, say,blog.py
. Because thetemplates
directory remains in themyproject
package, the templateasset specification
values inblog.py
must now be fully qualified with the project's package name (myproject:templates/blog.pt
).
You can then continue to add view callable functions to the blog.py
module, but you can also add other .py
files which contain view callable functions to the views
directory. As long as you use the @view_config
directive to register views in conjunction with config.scan()
, they will be picked up automatically when the application is restarted.
It is possible to use the pshell
command to load a Python interpreter prompt with a similar configuration as would be loaded if you were running your Pyramid application via pserve
. This can be a useful debugging tool. See interactive_shell
for more details.
The code generated by a Pyramid
scaffold assumes that you will be using the pserve
command to start your application while you do development. pserve
is a command that reads a PasteDeploy
.ini
file (e.g., development.ini
), and configures a server to serve a Pyramid
application based on the data in the file.
pserve
is by no means the only way to start up and serve a Pyramid
application. As we saw in firstapp_chapter
, pserve
needn't be invoked at all to run a Pyramid
application. The use of pserve
to run a Pyramid
application is purely conventional based on the output of its scaffolding. But we strongly recommend using pserve
while developing your application because many other convenience introspection commands (such as pviews
, prequest
, proutes
, and others) are also implemented in terms of configuration availability of this .ini
file format. It also configures Pyramid logging and provides the --reload
switch for convenient restarting of the server when code changes.
Pyramid scaffolds generate projects which use the Waitress
WSGI server. Waitress is a server that is suited for development and light production usage. It's not the fastest nor the most featureful WSGI server. Instead, its main feature is that it works on all platforms that Pyramid needs to run on, making it a good choice as a default server from the perspective of Pyramid's developers.
Any WSGI server is capable of running a Pyramid
application. But we suggest you stick with the default server for development, and that you wait to investigate other server options until you're ready to deploy your application to production. Unless for some reason you need to develop on a non-local system, investigating alternate server options is usually a distraction until you're ready to deploy. But we recommend developing using the default configuration on a local system that you have complete control over; it will provide the best development experience.
One popular production alternative to the default Waitress server is mod_wsgi
. You can use mod_wsgi
to serve your Pyramid
application using the Apache web server rather than any "pure-Python" server like Waitress. It is fast and featureful. See modwsgi_tutorial
for details.
Another good production alternative is Green Unicorn
(aka gunicorn
). It's faster than Waitress and slightly easier to configure than mod_wsgi
, although it depends, in its default configuration, on having a buffering HTTP proxy in front of it. It does not, as of this writing, work on Windows.