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130 lines
3.7 KiB
ReStructuredText
130 lines
3.7 KiB
ReStructuredText
##############
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Advanced usage
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##############
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This page describes some more advanced :mod:`cfig` features that you might be interested in using.
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Fail-fast
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=========
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If your variables are very slow to be resolved, you may want for the :meth:`~cfig.config.Configuration.ProxyDict.resolve` method to raise as soon as a single value fails to resolve.
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For that purpose, the :meth:`~cfig.config.Configuration.ProxyDict.resolve_failfast` method is provided:
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.. code-block:: python
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:emphasize-lines: 4
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from .mydefinitionmodule import config
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if __name__ == "__main__":
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config.proxies.resolve_failfast()
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Please note that the :meth:`~cfig.config.Configuration.ProxyDict.resolve_failfast` method does not raise :exc:`~cfig.errors.BatchResolutionFailure`, but raises the first occurring error instead, so you might want to catch it in this way:
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.. code-block:: python
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:emphasize-lines: 4,5,6,7
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from .mydefinitionmodule import config
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if __name__ == "__main__":
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try:
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config.proxies.resolve_failfast()
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except cfig.ConfigurationError as err:
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...
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Access all resolved variables at once
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=====================================
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In certain cases, you might want to obtain a :class:`dict` containing all resolved variables, without them being proxied.
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You may have noticed that both :meth:`~cfig.config.Configuration.ProxyDict.resolve` and :meth:`~cfig.config.Configuration.ProxyDict.resolve_failfast` return a :class:`dict`: that's exactly what you need!
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.. code-block:: python
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:emphasize-lines: 2
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...
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static_cfg = config.proxies.resolve()
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...
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.. note::
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Be aware that the :class:`dict` returned will never change, even after a :ref:`reload <Reloading variables>`!
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Reloading variables
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===================
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You might want for the configuration to be reloaded without restarting your application.
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In that case, you may use the :meth:`~cfig.config.Configuration.ProxyDict.unresolve` method to clear the cached values, and then call :meth:`~cfig.config.Configuration.ProxyDict.resolve` again.
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.. code-block:: python
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:emphasize-lines: 2,3
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...
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config.proxies.unresolve()
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config.proxies.resolve()
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...
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To reload a single variable, you may use the ``del`` keyword:
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.. code-block:: python
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:emphasize-lines: 2
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...
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del MY_VARIABLE.__wrapped__
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...
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Sources selection
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=================
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If you need further fine-tuning of the places to gather configuration values from, you may specify them via the :attr:`cfig.config.Configuration.sources` collection:
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.. code-block:: python
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:emphasize-lines: 2,3,5,6,7,8,9,10
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import cfig
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import cfig.sources.env
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import cfig.sources.envfile
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config = cfig.Configuration(sources=[
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cfig.source.env.EnvironmentSource(),
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cfig.source.env.EnvironmentSource(prefix="PROD_"),
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cfig.source.envfile.EnvironmentFileSource(),
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cfig.source.envfile.EnvironmentFileSource(suffix="_PATH"),
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])
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The specified sources are used in the order they are specified.
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They may also be altered at runtime, if for some *crazy reason* you need that feature:
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.. code-block:: python
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:emphasize-lines: 6,7,8
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import cfig
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import cfig.sources.env
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config = cfig.Configuration()
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config.sources.append(
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cfig.source.env.EnvironmentSource()
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)
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.. note::
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Already cached variables **won't** be automatically reloaded after changing the sources!
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Sources customization
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---------------------
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If the provided sources aren't enough, you may create a custom class inheriting from :class:`~cfig.sources.base.Source`.
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.. hint::
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Since :mod:`cfig.sources` is a namespace package, if you intend to distribute your custom source, you may want to do it by extending the namespace, for an easier developer workflow.
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