path: root/docs/narr/environment.rst

.. index::
   single: environment variables
   single: settings
   single: reload
   single: debug_authorization
   single: reload_assets
   single: debug_notfound
   single: debug_all
   single: reload_all
   single: debug settings
   single: debug_routematch
   single: prevent_http_cache
   single: reload settings
   single: default_locale_name
   single: environment variables
   single: Mako environment settings
   single: ini file settings
   single: PasteDeploy settings

.. _environment_chapter:

Environment Variables and ``.ini`` File Settings
================================================

:app:`Pyramid` behavior can be configured through a combination of
operating system environment variables and ``.ini`` configuration file
application section settings.  The meaning of the environment
variables and the configuration file settings overlap.

.. note:: Where a configuration file setting exists with the same
          meaning as an environment variable, and both are present at
          application startup time, the environment variable setting
          takes precedence.

The term "configuration file setting name" refers to a key in the
``.ini`` configuration for your application.  The configuration file
setting names documented in this chapter are reserved for
:app:`Pyramid` use.  You should not use them to indicate
application-specific configuration settings.

Reloading Templates
-------------------

When this value is true, templates are automatically reloaded whenever
they are modified without restarting the application, so you can see
changes to templates take effect immediately during development.  This
flag is meaningful to Chameleon and Mako templates, as well as most
third-party template rendering extensions.

+---------------------------------+--------------------------------+
| Environment Variable Name       | Config File Setting Name       |
+=================================+================================+
| ``PYRAMID_RELOAD_TEMPLATES``    |  ``pyramid.reload_templates``  |
|                                 |                                |
|                                 |                                |
|                                 |                                |
+---------------------------------+--------------------------------+

Reloading Assets
----------------

Don't cache any asset file data when this value is true.  See
also :ref:`overriding_assets_section`.

+---------------------------------+-----------------------------+
| Environment Variable Name       | Config File Setting Name    |
+=================================+=============================+
| ``PYRAMID_RELOAD_ASSETS``       |  ``pyramid.reload_assets``  |
|                                 |                             |
|                                 |                             |
|                                 |                             |
+---------------------------------+-----------------------------+

.. note:: For backwards compatibility purposes, aliases can be
   used for configurating asset reloading: ``PYRAMID_RELOAD_RESOURCES`` (envvar)
   and ``pyramid.reload_resources`` (config file).

Debugging Authorization
-----------------------

Print view authorization failure and success information to stderr
when this value is true.  See also :ref:`debug_authorization_section`.

+---------------------------------+-----------------------------------+
| Environment Variable Name       | Config File Setting Name          |
+=================================+===================================+
| ``PYRAMID_DEBUG_AUTHORIZATION`` |  ``pyramid.debug_authorization``  |
|                                 |                                   |
|                                 |                                   |
|                                 |                                   |
+---------------------------------+-----------------------------------+

Debugging Not Found Errors
--------------------------

Print view-related ``NotFound`` debug messages to stderr
when this value is true.  See also :ref:`debug_notfound_section`.

+---------------------------------+------------------------------+
| Environment Variable Name       | Config File Setting Name     |
+=================================+==============================+
| ``PYRAMID_DEBUG_NOTFOUND``      |  ``pyramid.debug_notfound``  |
|                                 |                              |
|                                 |                              |
|                                 |                              |
+---------------------------------+------------------------------+

Debugging Route Matching
------------------------

Print debugging messages related to :term:`url dispatch` route matching when
this value is true.  See also :ref:`debug_routematch_section`.

+---------------------------------+--------------------------------+
| Environment Variable Name       | Config File Setting Name       |
+=================================+================================+
| ``PYRAMID_DEBUG_ROUTEMATCH``    |  ``pyramid.debug_routematch``  |
|                                 |                                |
|                                 |                                |
|                                 |                                |
+---------------------------------+--------------------------------+

.. _preventing_http_caching:

Preventing HTTP Caching
------------------------

Prevent the ``http_cache`` view configuration argument from having any effect
globally in this process when this value is true.  No http caching-related
response headers will be set by the Pyramid ``http_cache`` view configuration
feature when this is true.  See also :ref:`influencing_http_caching`.

+---------------------------------+----------------------------------+
| Environment Variable Name       | Config File Setting Name         |
+=================================+==================================+
| ``PYRAMID_PREVENT_HTTP_CACHE``  |  ``pyramid.prevent_http_cache``  |
|                                 |                                  |
|                                 |                                  |
|                                 |                                  |
+---------------------------------+----------------------------------+

Debugging All
-------------

Turns on all ``debug*`` settings.

+---------------------------------+-----------------------------+
| Environment Variable Name       | Config File Setting Name    |
+=================================+=============================+
| ``PYRAMID_DEBUG_ALL``           |  ``pyramid.debug_all``      |
|                                 |                             |
|                                 |                             |
|                                 |                             |
+---------------------------------+-----------------------------+

Reloading All
-------------

Turns on all ``reload*`` settings.

+---------------------------------+-----------------------------+
| Environment Variable Name       | Config File Setting Name    |
+=================================+=============================+
| ``PYRAMID_RELOAD_ALL``          |  ``pyramid.reload_all``     |
|                                 |                             |
|                                 |                             |
|                                 |                             |
+---------------------------------+-----------------------------+

.. _default_locale_name_setting:

Default Locale Name
--------------------

The value supplied here is used as the default locale name when a
:term:`locale negotiator` is not registered.  See also
:ref:`localization_deployment_settings`.

+---------------------------------+-----------------------------------+
| Environment Variable Name       | Config File Setting Name          |
+=================================+===================================+
| ``PYRAMID_DEFAULT_LOCALE_NAME`` |  ``pyramid.default_locale_name``  |
|                                 |                                   |
|                                 |                                   |
|                                 |                                   |
+---------------------------------+-----------------------------------+

Including Packages
------------------

``pyramid.includes`` instructs your application to include other packages.
Using the setting is equivalent to using the
:meth:`pyramid.config.Configurator.include` method.  

+---------------------------------+
| Config File Setting Name        |
+=================================+
| ``pyramid.includes``            |
|                                 |
|                                 |
|                                 |
+---------------------------------+

The value supplied as ``pyramid.includes`` should be a sequence.  The
sequence can take several different forms.

1) It can be a string.

   If it is a string, the package names can be separated by spaces::

      package1 package2 package3

    The package names can also be separated by carriage returns::

       package1
       package2
       package3

2) It can be a Python list, where the values are strings::

   ['package1', 'package2', 'package3']

Each value in the sequence should be a :term:`dotted Python name`.

``pyramid.includes`` vs. :meth:`pyramid.config.Configurator.include`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Two methods exist for including packages: ``pyramid.includes`` and
:meth:`pyramid.config.Configurator.include`.  This section explains their
equivalence.

Using PasteDeploy
+++++++++++++++++

Using the following ``pyramid.includes`` setting in the PasteDeploy ``.ini``
file in your application:

.. code-block:: ini

   [app:myapp]
   pyramid.includes = pyramid_debugtoolbar
                      pyramid_tm

Is equivalent to using the following statements in your configuration code:

.. code-block:: python
   :linenos:

   from pyramid.config import Configurator

   def main(global_config, **settings):
       config = Configurator(settings=settings)
       # ...
       config.include('pyramid_debugtoolbar')
       config.include('pyramid_tm')
       # ...

It is fine to use both or either form.

Plain Python
++++++++++++

Using the following ``pyramid.includes`` setting in your plain-Python Pyramid
application: 

.. code-block:: python
   :linenos:

   from pyramid.config import Configurator

   if __name__ == '__main__':
       settings = {'pyramid.includes':'pyramid_debugtoolbar pyramid_tm'}
       config = Configurator(settings=settings)

Is equivalent to using the following statements in your configuration code:

.. code-block:: python
   :linenos:

   from pyramid.config import Configurator

   if __name__ == '__main__':
       settings = {}
       config = Configurator(settings=settings)
       config.include('pyramid_debugtoolbar')
       config.include('pyramid_tm')

It is fine to use both or either form.

Explicit Tween Configuration
----------------------------

This value allows you to perform explicit :term:`tween` ordering in your
configuration.  Tweens are bits of code used by add-on authors to extend
Pyramid.  They form a chain, and require ordering.

Ideally, you won't need to use the ``pyramid.tweens`` setting at all.  Tweens
are generally ordered and included "implicitly" when an add-on package which
registers a tween is "included".  Packages are included when you name a
``pyramid.includes`` setting in your configuration or when you call
:meth:`pyramid.config.Configuration.include`.

Authors of included add-ons provide "implicit" tween configuration ordering
hints to Pyramid when their packages are included.  However, the implicit
tween ordering is only best-effort.  Pyramid will attempt to provide an
implicit order of tweens as best it can using hints provided by add-on
authors, but because it's only best-effort, if very precise tween ordering is
required, the only surefire way to get it is to use an explicit tween order.
You may be required to inspect your tween ordering (see
:ref:`displaying_tweens`) and add a ``pyramid.tweens`` configuration value at
the behest of an add-on author.

+---------------------------------+
| Config File Setting Name        |
+=================================+
| ``pyramid.tweens``              |
|                                 |
|                                 |
|                                 |
+---------------------------------+

The value supplied as ``pyramid.tweens`` should be a sequence.  The
sequence can take several different forms.

1) It can be a string.

   If it is a string, the tween names can be separated by spaces::

      pkg.tween_factory1 pkg.tween_factory2 pkg.tween_factory3

    The tween names can also be separated by carriage returns::

       pkg.tween_factory1
       pkg.tween_factory2
       pkg.tween_factory3

2) It can be a Python list, where the values are strings::

   ['pkg.tween_factory1', 'pkg.tween_factory2', 'pkg.tween_factory3']

Each value in the sequence should be a :term:`dotted Python name`.

Paste Configuration vs. Plain-Python Configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Using the following ``pyramid.tweens`` setting in the PasteDeploy ``.ini``
file in your application:

.. code-block:: ini

   [app:myapp]
   pyramid.tweens = pyramid_debugtoolbar.toolbar.tween_factory
                    pyramid.tweens.excview_tween_factory
                    pyramid_tm.tm_tween_factory

Is equivalent to using the following statements in your configuration code:

.. code-block:: python
   :linenos:

   from pyramid.config import Configurator
 
   def main(global_config, **settings):
       settings['pyramid.tweens'] = [
               'pyramid_debugtoolbar.toolbar.tween_factory',
               'pyramid.tweebs.excview_tween_factory',
               'pyramid_tm.tm_tween_factory',
                ]
       config = Configurator(settings=settings)

It is fine to use both or either form.

.. _mako_template_renderer_settings:

Mako Template Render Settings
-----------------------------

Mako derives additional settings to configure its template renderer that
should be set when using it. Many of these settings are optional and only need
to be set if they should be different from the default. The Mako Template
Renderer uses a subclass of Mako's `template lookup
<http://www.makotemplates.org/docs/usage.html#usage_lookup>`_ and accepts
several arguments to configure it.

Mako Directories
~~~~~~~~~~~~~~~~

The value(s) supplied here are passed in as the template directories. They
should be in :term:`asset specification` format, for example:
``my.package:templates``.

+-----------------------------+
| Config File Setting Name    |
+=============================+
|  ``mako.directories``       |
|                             |
|                             |
|                             |
+-----------------------------+

Mako Module Directory
~~~~~~~~~~~~~~~~~~~~~

The value supplied here tells Mako where to store compiled Mako templates. If
omitted, compiled templates will be stored in memory. This value should be an
absolute path, for example: ``%(here)s/data/templates`` would use a directory
called ``data/templates`` in the same parent directory as the INI file.

+-----------------------------+
| Config File Setting Name    |
+=============================+
|  ``mako.module_directory``  |
|                             |
|                             |
|                             |
+-----------------------------+

Mako Input Encoding
~~~~~~~~~~~~~~~~~~~

The encoding that Mako templates are assumed to have. By default this is set
to ``utf-8``. If you wish to use a different template encoding, this value
should be changed accordingly.

+-----------------------------+
| Config File Setting Name    |
+=============================+
|  ``mako.input_encoding``    |
|                             |
|                             |
|                             |
+-----------------------------+

Mako Error Handler
~~~~~~~~~~~~~~~~~~

A callable (or a :term:`dotted Python name` which names a callable) which is
called whenever Mako compile or runtime exceptions occur. The callable is
passed the current context as well as the exception. If the callable returns
True, the exception is considered to be handled, else it is re-raised after
the function completes. Is used to provide custom error-rendering functions.

+-----------------------------+
| Config File Setting Name    |
+=============================+
|  ``mako.error_handler``     |
|                             |
|                             |
|                             |
+-----------------------------+

Mako Default Filters
~~~~~~~~~~~~~~~~~~~~

List of string filter names that will be applied to all Mako expressions.

+-----------------------------+
| Config File Setting Name    |
+=============================+
|  ``mako.default_filters``   |
|                             |
|                             |
|                             |
+-----------------------------+

Mako Import
~~~~~~~~~~~

String list of Python statements, typically individual "import" lines, which
will be placed into the module level preamble of all generated Python modules.


+-----------------------------+
| Config File Setting Name    |
+=============================+
|  ``mako.imports``           |
|                             |
|                             |
|                             |
+-----------------------------+


Mako Strict Undefined
~~~~~~~~~~~~~~~~~~~~~

``true`` or ``false``, representing the "strict undefined" behavior of Mako
(see `Mako Context Variables
<http://www.makotemplates.org/docs/runtime.html#context-variables>`_).  By
default, this is ``false``.

+-----------------------------+
| Config File Setting Name    |
+=============================+
|  ``mako.strict_undefined``  |
|                             |
|                             |
|                             |
+-----------------------------+

Mako Preprocessor
~~~~~~~~~~~~~~~~~

A callable (or a :term:`dotted Python name` which names a callable) which is
called to preprocess the source before the template is called.  The callable
will be passed the full template source before it is parsed. The return
result of the callable will be used as the template source code.

.. note:: This feature is new in Pyramid 1.1.

+-----------------------------+
| Config File Setting Name    |
+=============================+
|  ``mako.preprocessor``      |
|                             |
|                             |
|                             |
+-----------------------------+

Examples
--------

Let's presume your configuration file is named ``MyProject.ini``, and
there is a section representing your application named ``[app:main]``
within the file that represents your :app:`Pyramid` application.
The configuration file settings documented in the above "Config File
Setting Name" column would go in the ``[app:main]`` section.  Here's
an example of such a section:

.. code-block:: ini
  :linenos:

  [app:main]
  use = egg:MyProject#app
  pyramid.reload_templates = true
  pyramid.debug_authorization = true

You can also use environment variables to accomplish the same purpose
for settings documented as such.  For example, you might start your
:app:`Pyramid` application using the following command line:

.. code-block:: text

  $ PYRAMID_DEBUG_AUTHORIZATION=1 PYRAMID_RELOAD_TEMPLATES=1 \
         bin/paster serve MyProject.ini

If you started your application this way, your :app:`Pyramid`
application would behave in the same manner as if you had placed the
respective settings in the ``[app:main]`` section of your
application's ``.ini`` file.

If you want to turn all ``debug`` settings (every setting that starts
with ``pyramid.debug_``). on in one fell swoop, you can use
``PYRAMID_DEBUG_ALL=1`` as an environment variable setting or you may use
``pyramid.debug_all=true`` in the config file.  Note that this does not affect
settings that do not start with ``pyramid.debug_*`` such as
``pyramid.reload_templates``.

If you want to turn all ``pyramid.reload`` settings (every setting that starts
with ``pyramid.reload_``) on in one fell swoop, you can use
``PYRAMID_RELOAD_ALL=1`` as an environment variable setting or you may use
``pyramid.reload_all=true`` in the config file.  Note that this does not
affect settings that do not start with ``pyramid.reload_*`` such as
``pyramid.debug_notfound``.

.. note::
   Specifying configuration settings via environment variables is generally
   most useful during development, where you may wish to augment or
   override the more permanent settings in the configuration file.
   This is useful because many of the reload and debug settings may
   have performance or security (i.e., disclosure) implications
   that make them undesirable in a production environment.

.. index::
   single: reload_templates
   single: reload_assets

Understanding the Distinction Between ``reload_templates`` and ``reload_assets``
--------------------------------------------------------------------------------

The difference between ``pyramid.reload_assets`` and
``pyramid.reload_templates`` is a bit subtle. Templates are themselves also
treated by :app:`Pyramid` as asset files (along with other static files), so the
distinction can be confusing.  It's helpful to read
:ref:`overriding_assets_section` for some context about assets in general.

When ``pyramid.reload_templates`` is true, :app:`Pyramid` takes advantage of the
underlying templating systems' ability to check for file modifications to an
individual template file.  When ``pyramid.reload_templates`` is true but
``pyramid.reload_assets`` is *not* true, the template filename returned by the
``pkg_resources`` package (used under the hood by asset resolution) is cached
by :app:`Pyramid` on the first request.  Subsequent requests for the same
template file will return a cached template filename.  The underlying
templating system checks for modifications to this particular file for every
request.  Setting ``pyramid.reload_templates`` to ``True`` doesn't affect
performance dramatically (although it should still not be used in production
because it has some effect).

However, when ``pyramid.reload_assets`` is true, :app:`Pyramid` will not cache
the template filename, meaning you can see the effect of changing the content
of an overridden asset directory for templates without restarting the server
after every change.  Subsequent requests for the same template file may
return different filenames based on the current state of overridden asset
directories. Setting ``pyramid.reload_assets`` to ``True`` affects performance
*dramatically*, slowing things down by an order of magnitude for each
template rendering.  However, it's convenient to enable when moving files
around in overridden asset directories. ``pyramid.reload_assets`` makes the
system *very slow* when templates are in use.  Never set
``pyramid.reload_assets`` to ``True`` on a production system.

.. index::
   par: settings; adding custom

.. _adding_a_custom_setting:

Adding A Custom Setting
-----------------------

From time to time, you may need to add a custom setting to your application.
Here's how:

- If you're using an ``.ini`` file, change the ``.ini`` file, adding the
  setting to the ``[app:foo]`` section representing your Pyramid application.
  For example:

  .. code-block:: ini

    [app:myapp]
    # .. other settings
    debug_frobnosticator = True

- In the ``main()`` function that represents the place that your Pyramid WSGI
  application is created, anticipate that you'll be getting this key/value
  pair as a setting and do any type conversion necessary.

  If you've done any type conversion of your custom value, reset the
  converted values into the ``settings`` dictionary *before* you pass the
  dictionary as ``settings`` to the :term:`Configurator`.  For example:

  .. code-block:: python

     def main(global_config, **settings):
         # ...
         from pyramid.settings import asbool
         debug_frobnosticator = asbool(settings.get(
                    'debug_frobnosticator', 'false'))
         settings['debug_frobnosticator'] = debug_frobnosticator
         config = Configurator(settings=settings)

  .. note:: It's especially important that you mutate the ``settings``
     dictionary with the converted version of the variable *before* passing
     it to the Configurator: the configurator makes a *copy* of ``settings``,
     it doesn't use the one you pass directly.

- In the runtime code that you need to access the new settings value, find
  the value in the ``registry.settings`` dictionary and use it.  In
  :term:`view` code (or any other code that has access to the request), the
  easiest way to do this is via ``request.registry.settings``.  For example:

  .. code-block:: python

     registry = request.registry.settings
     debug_frobnosticator = settings['debug_frobnosticator']

  If you wish to use the value in code that does not have access to the
  request and you wish to use the value, you'll need to use the
  :func:`pyramid.threadlocal.get_current_registry` API to obtain the current
  registry, then ask for its ``settings`` attribute.  For example:

  .. code-block:: python

     registry = pyramid.threadlocal.get_current_registry()
     settings = registry.settings
     debug_frobnosticator = settings['debug_frobnosticator']