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164 lines
5.3 KiB
ReStructuredText
164 lines
5.3 KiB
ReStructuredText
.. _configuration-provider:
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Configuration provider
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======================
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.. meta::
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:keywords: Python,DI,Dependency injection,IoC,Inversion of Control,Configuration,Injection,
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Option,Ini,Json,Yaml,Dict,Environment Variable,Load,Read,Get
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:description: Configuration provides configuration options to the other providers. This page
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demonstrates how to use Configuration provider to inject the dependencies, load
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a configuration from an ini or yaml file, dictionary or an environment variable.
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.. currentmodule:: dependency_injector.providers
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:py:class:`Configuration` provider provides configuration options to the other providers.
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.. literalinclude:: ../../examples/providers/configuration/configuration.py
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:language: python
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:emphasize-lines: 7,12-13
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:lines: 3-
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It implements the principle "use first, define later".
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Loading from an INI file
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------------------------
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``Configuration`` provider can load configuration from an ``ini`` file using the
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:py:meth:`Configuration.from_ini` method:
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.. literalinclude:: ../../examples/providers/configuration/configuration_ini.py
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:language: python
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:lines: 3-
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:emphasize-lines: 12
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where ``examples/providers/configuration/config.ini`` is:
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.. literalinclude:: ../../examples/providers/configuration/config.ini
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:language: ini
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:py:meth:`Configuration.from_ini` method supports environment variables interpolation. Use
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``${ENV_NAME}`` format in the configuration file to substitute value of the environment
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variable ``ENV_NAME``.
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Loading from a YAML file
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------------------------
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``Configuration`` provider can load configuration from a ``yaml`` file using the
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:py:meth:`Configuration.from_yaml` method:
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.. literalinclude:: ../../examples/providers/configuration/configuration_yaml.py
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:language: python
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:lines: 3-
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:emphasize-lines: 12
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where ``examples/providers/configuration/config.yml`` is:
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.. literalinclude:: ../../examples/providers/configuration/config.yml
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:language: ini
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:py:meth:`Configuration.from_yaml` method supports environment variables interpolation. Use
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``${ENV_NAME}`` format in the configuration file to substitute value of the environment
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variable ``ENV_NAME``.
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.. note::
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Loading of a yaml configuration requires ``PyYAML`` package.
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You can install the ``Dependency Injector`` with an extra dependency::
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pip install dependency-injector[yaml]
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or install ``PyYAML`` directly::
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pip install pyyaml
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*Don't forget to mirror the changes in the requirements file.*
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Loading from a dictionary
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-------------------------
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``Configuration`` provider can load configuration from a Python ``dict`` using the
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:py:meth:`Configuration.from_dict` method:
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.. literalinclude:: ../../examples/providers/configuration/configuration_dict.py
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:language: python
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:lines: 3-
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:emphasize-lines: 12-19
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Loading from an environment variable
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------------------------------------
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``Configuration`` provider can load configuration from an environment variable using the
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:py:meth:`Configuration.from_env` method:
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.. literalinclude:: ../../examples/providers/configuration/configuration_env.py
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:language: python
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:lines: 3-
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:emphasize-lines: 18-20
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Loading from the multiple sources
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---------------------------------
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``Configuration`` provider can load configuration from the multiple sources. Loaded
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configuration is merged recursively over the existing configuration.
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.. literalinclude:: ../../examples/providers/configuration/configuration_multiple.py
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:language: python
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:lines: 3-
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:emphasize-lines: 12-13
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where ``examples/providers/configuration/config.local.yml`` is:
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.. literalinclude:: ../../examples/providers/configuration/config.local.yml
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:language: ini
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Specifying the value type
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-------------------------
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You can specify the type of the injected configuration value explicitly.
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This helps when you read the value from an ini file or an environment variable and need to
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convert it into an ``int`` or a ``float``.
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.. literalinclude:: ../../examples/providers/configuration/configuration_type.py
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:language: python
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:lines: 3-
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:emphasize-lines: 19
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``Configuration`` provider has next helper methods:
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- ``.as_int()``
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- ``.as_float()``
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- ``.as_(callback, *args, **kwargs)``
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The last method ``.as_(callback, *args, **kwargs)`` helps to implement other conversions.
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.. literalinclude:: ../../examples/providers/configuration/configuration_type_custom.py
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:language: python
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:lines: 3-
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:emphasize-lines: 18
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With the ``.as_(callback, *args, **kwargs)`` you can specify a function that will be called
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before the injection. The value from the config will be passed as a first argument. The returned
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value will be injected. Parameters ``*args`` and ``**kwargs`` are handled as any other injections.
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Injecting invariants
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--------------------
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You can inject invariant configuration options based on the value of the other configuration
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option.
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To use that you should provide the switch-value as an item of the configuration option that
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contains sections ``config.options[config.switch]``:
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- When the value of the ``config.switch`` is ``A``, the ``config.options.A`` is injected
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- When the value of the ``config.switch`` is ``B``, the ``config.options.B`` is injected
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.. literalinclude:: ../../examples/providers/configuration/configuration_itemselector.py
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:language: python
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:lines: 3-
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:emphasize-lines: 15,30-31,38
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.. disqus::
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