8.4 KiB
Core API
This section documents the Scrapy core API, and it's intended for developers of extensions and middlewares.
Crawler API
The main entry point to the Scrapy API is the :class:`~scrapy.crawler.Crawler` object, which :ref:`components <topics-components>` can :ref:`get for initialization <from-crawler>`. It provides access to all Scrapy core components, and it is the only way for components to access them and hook their functionality into Scrapy.
System Message: ERROR/3 (<stdin>, line 15); backlink
Unknown interpreted text role "class".System Message: ERROR/3 (<stdin>, line 15); backlink
Unknown interpreted text role "ref".System Message: ERROR/3 (<stdin>, line 15); backlink
Unknown interpreted text role "ref".System Message: ERROR/3 (<stdin>, line 21)
Unknown directive type "module".
.. module:: scrapy.crawler :synopsis: The Scrapy crawler
The Extension Manager is responsible for loading and keeping track of installed extensions and it's configured through the :setting:`EXTENSIONS` setting which contains a dictionary of all available extensions and their order similar to how you :ref:`configure the downloader middlewares <topics-downloader-middleware-setting>`.
System Message: ERROR/3 (<stdin>, line 24); backlink
Unknown interpreted text role "setting".System Message: ERROR/3 (<stdin>, line 24); backlink
Unknown interpreted text role "ref".System Message: ERROR/3 (<stdin>, line 30)
Unknown directive type "autoclass".
.. autoclass:: Crawler
:members: get_addon, get_downloader_middleware, get_extension,
get_item_pipeline, get_spider_middleware
The Crawler object must be instantiated with a
:class:`scrapy.Spider` subclass and a
:class:`scrapy.settings.Settings` object.
.. attribute:: request_fingerprinter
The request fingerprint builder of this crawler.
This is used from extensions and middlewares to build short, unique
identifiers for requests. See :ref:`request-fingerprints`.
.. attribute:: settings
The settings manager of this crawler.
This is used by extensions & middlewares to access the Scrapy settings
of this crawler.
For an introduction on Scrapy settings see :ref:`topics-settings`.
For the API see :class:`~scrapy.settings.Settings` class.
.. attribute:: signals
The signals manager of this crawler.
This is used by extensions & middlewares to hook themselves into Scrapy
functionality.
For an introduction on signals see :ref:`topics-signals`.
For the API see :class:`~scrapy.signalmanager.SignalManager` class.
.. attribute:: stats
The stats collector of this crawler.
This is used from extensions & middlewares to record stats of their
behaviour, or access stats collected by other extensions.
For an introduction on stats collection see :ref:`topics-stats`.
For the API see :class:`~scrapy.statscollectors.StatsCollector` class.
.. attribute:: extensions
The extension manager that keeps track of enabled extensions.
Most extensions won't need to access this attribute.
For an introduction on extensions and a list of available extensions on
Scrapy see :ref:`topics-extensions`.
.. attribute:: engine
The execution engine, which coordinates the core crawling logic
between the scheduler, downloader and spiders.
Some extension may want to access the Scrapy engine, to inspect or
modify the downloader and scheduler behaviour, although this is an
advanced use and this API is not yet stable.
.. attribute:: spider
Spider currently being crawled. This is an instance of the spider class
provided while constructing the crawler, and it is created after the
arguments given in the :meth:`crawl` method.
.. method:: crawl(*args, **kwargs)
Starts the crawler by instantiating its spider class with the given
``args`` and ``kwargs`` arguments, while setting the execution engine in
motion. Should be called only once.
Returns a deferred that is fired when the crawl is finished.
.. automethod:: stop
System Message: ERROR/3 (<stdin>, line 112)
Unknown directive type "autoclass".
.. autoclass:: CrawlerRunner :members:
System Message: ERROR/3 (<stdin>, line 115)
Unknown directive type "autoclass".
.. autoclass:: CrawlerProcess :show-inheritance: :members: :inherited-members:
Settings API
System Message: ERROR/3 (<stdin>, line 125)
Unknown directive type "module".
.. module:: scrapy.settings :synopsis: Settings manager
System Message: ERROR/3 (<stdin>, line 128)
Unknown directive type "attribute".
.. attribute:: SETTINGS_PRIORITIES
Dictionary that sets the key name and priority level of the default
settings priorities used in Scrapy.
Each item defines a settings entry point, giving it a code name for
identification and an integer priority. Greater priorities take more
precedence over lesser ones when setting and retrieving values in the
:class:`~scrapy.settings.Settings` class.
.. code-block:: python
SETTINGS_PRIORITIES = {
"default": 0,
"command": 10,
"addon": 15,
"project": 20,
"spider": 30,
"cmdline": 40,
}
For a detailed explanation on each settings sources, see:
:ref:`topics-settings`.
System Message: ERROR/3 (<stdin>, line 152)
Unknown directive type "autofunction".
.. autofunction:: get_settings_priority
System Message: ERROR/3 (<stdin>, line 154)
Unknown directive type "autoclass".
.. autoclass:: Settings :show-inheritance: :members:
System Message: ERROR/3 (<stdin>, line 158)
Unknown directive type "autoclass".
.. autoclass:: BaseSettings :members:
SpiderLoader API
System Message: ERROR/3 (<stdin>, line 166)
Unknown directive type "module".
.. module:: scrapy.spiderloader :synopsis: The spider loader
This class is in charge of retrieving and handling the spider classes defined across the project.
Custom spider loaders can be employed by specifying their path in the :setting:`SPIDER_LOADER_CLASS` project setting. They must fully implement the :class:`scrapy.interfaces.ISpiderLoader` interface to guarantee an errorless execution.
System Message: ERROR/3 (<stdin>, line 174); backlink
Unknown interpreted text role "setting".System Message: ERROR/3 (<stdin>, line 174); backlink
Unknown interpreted text role "class".System Message: ERROR/3 (<stdin>, line 179)
Unknown directive type "method".
.. method:: from_settings(settings) This class method is used by Scrapy to create an instance of the class. It's called with the current project settings, and it loads the spiders found recursively in the modules of the :setting:`SPIDER_MODULES` setting. :param settings: project settings :type settings: :class:`~scrapy.settings.Settings` instance
System Message: ERROR/3 (<stdin>, line 189)
Unknown directive type "method".
.. method:: load(spider_name) Get the Spider class with the given name. It'll look into the previously loaded spiders for a spider class with name ``spider_name`` and will raise a KeyError if not found. :param spider_name: spider class name :type spider_name: str
System Message: ERROR/3 (<stdin>, line 198)
Unknown directive type "method".
.. method:: list() Get the names of the available spiders in the project.
System Message: ERROR/3 (<stdin>, line 202)
Unknown directive type "method".
.. method:: find_by_request(request) List the spiders' names that can handle the given request. Will try to match the request's url against the domains of the spiders. :param request: queried request :type request: :class:`~scrapy.Request` instance
Signals API
System Message: ERROR/3 (<stdin>, line 215)
Unknown directive type "automodule".
.. automodule:: scrapy.signalmanager
:synopsis: The signal manager
:members:
:undoc-members:
Stats Collector API
There are several Stats Collectors available under the :mod:`scrapy.statscollectors` module and they all implement the Stats Collector API defined by the :class:`~scrapy.statscollectors.StatsCollector` class (which they all inherit from).
System Message: ERROR/3 (<stdin>, line 225); backlink
Unknown interpreted text role "mod".System Message: ERROR/3 (<stdin>, line 225); backlink
Unknown interpreted text role "class".System Message: ERROR/3 (<stdin>, line 230)
Unknown directive type "module".
.. module:: scrapy.statscollectors :synopsis: Stats Collectors
System Message: ERROR/3 (<stdin>, line 235)
Unknown directive type "method".
.. method:: get_value(key, default=None)
Return the value for the given stats key or default if it doesn't exist.
System Message: ERROR/3 (<stdin>, line 239)
Unknown directive type "method".
.. method:: get_stats()
Get all stats from the currently running spider as a dict.
System Message: ERROR/3 (<stdin>, line 243)
Unknown directive type "method".
.. method:: set_value(key, value)
Set the given value for the given stats key.
System Message: ERROR/3 (<stdin>, line 247)
Unknown directive type "method".
.. method:: set_stats(stats)
Override the current stats with the dict passed in ``stats`` argument.
System Message: ERROR/3 (<stdin>, line 251)
Unknown directive type "method".
.. method:: inc_value(key, count=1, start=0)
Increment the value of the given stats key, by the given count,
assuming the start value given (when it's not set).
System Message: ERROR/3 (<stdin>, line 256)
Unknown directive type "method".
.. method:: max_value(key, value)
Set the given value for the given key only if current value for the
same key is lower than value. If there is no current value for the
given key, the value is always set.
System Message: ERROR/3 (<stdin>, line 262)
Unknown directive type "method".
.. method:: min_value(key, value)
Set the given value for the given key only if current value for the
same key is greater than value. If there is no current value for the
given key, the value is always set.
System Message: ERROR/3 (<stdin>, line 268)
Unknown directive type "method".
.. method:: clear_stats()
Clear all stats.
The following methods are not part of the stats collection api but instead used when implementing custom stats collectors:
System Message: ERROR/3 (<stdin>, line 275)
Unknown directive type "method".
.. method:: open_spider(spider)
Open the given spider for stats collection.
System Message: ERROR/3 (<stdin>, line 279)
Unknown directive type "method".
.. method:: close_spider(spider)
Close the given spider. After this is called, no more specific stats
can be accessed or collected.
Engine API
System Message: ERROR/3 (<stdin>, line 287)
Unknown directive type "autoclass".
.. autoclass:: scrapy.core.engine.ExecutionEngine() :members: needs_backout