mirror of https://github.com/scrapy/scrapy.git
70 lines
2.0 KiB
ReStructuredText
70 lines
2.0 KiB
ReStructuredText
.. _topics-addons:
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=======
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Add-ons
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=======
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Scrapy's add-on system is a framework which unifies managing and configuring
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components that extend Scrapy's core functionality, such as middlewares,
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extensions, or pipelines. It provides users with a plug-and-play experience in
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Scrapy extension management, and grants extensive configuration control to
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developers.
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Activating and configuring add-ons
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==================================
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Add-ons and their configuration live in Scrapy's
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:class:`~scrapy.addons.AddonManager`. During a :class:`~scrapy.crawler.Crawler`
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initialization the add-on manager will read a list of enabled add-ons from your
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``ADDONS`` setting.
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The ``ADDONS`` setting is a dict in which every key is an addon class or its
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import path and the value is its priority.
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This is an example where two add-ons are enabled in a project's
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``settings.py``::
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ADDONS = {
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'path.to.someaddon': 0,
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path.to.someaddon2: 1,
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}
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Writing your own add-ons
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========================
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Add-ons are (any) Python *objects* that include the following method:
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.. method:: update_settings(settings)
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This method is called during the initialization of the
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:class:`~scrapy.crawler.Crawler`. Here, you should perform dependency checks
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(e.g. for external Python libraries) and update the
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:class:`~scrapy.settings.Settings` object as wished, e.g. enable components
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for this add-on or set required configuration of other extensions.
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:param settings: The settings object storing Scrapy/component configuration
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:type settings: :class:`~scrapy.settings.Settings`
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Add-on examples
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===============
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Set some basic configuration::
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class MyAddon:
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def update_settings(self, settings):
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settings["ITEM_PIPELINES"]["path.to.mypipeline"] = 200
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settings["DNSCACHE_ENABLED"] = True
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Check dependencies::
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class MyAddon:
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def update_settings(self, settings):
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try:
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import boto
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except ImportError:
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raise RuntimeError("MyAddon requires the boto library")
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...
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