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adding spider args as attrs to docs #1719

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adding spider args as attrs to docs #1719

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14 changes: 13 additions & 1 deletion docs/topics/spiders.rst
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Expand Up @@ -283,7 +283,19 @@ Spider arguments are passed through the :command:`crawl` command using the

scrapy crawl myspider -a category=electronics

Spiders receive arguments in their constructors::
Spider arguments are exposed as attributes::
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Hey @demelziraptor !
This is about documenting the feature of spider arguments being exposed as attributes, right? (this line: https://github.com/scrapy/scrapy/blob/master/scrapy/spiders/__init__.py#L30)

From the example it isn't clear what this is trying to show.

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Exactly @eliasdorneles, from the current docs it seems like the only way to access spider input arguments is from the constructor arguments.

Maybe this example is better?

    import scrapy

    class MySpider(scrapy.Spider):
        name = 'myspider'

        def parse(self, response):
            products = response.css('.%s' % self.category)

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Hm, I think it'll need more than an example.
Looking at the example alone it looks like broken code. :)

Perhaps adding a default as a class attribute, like:

import scrapy

class MySpider(scrapy.Spider):
    name = 'myspider'
    category = 'default-category'  # use -a category=another from the cmdline to override this

    def parse(self, response):
        products = response.css('.%s' % self.category)

This may deserve its own section in the docs really. :)

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I would suggest to add a spider that can be copied, ran with runspider and get a result; something somehow interactive. Doesn't need to browse, it can do some comparison and close, maybe using start_requests or adding a signal.


import scrapy

class MySpider(scrapy.Spider):
name = 'myspider'

def __init__(self, *args, **kwargs):
super(MySpider, self).__init__(*args, **kwargs)
self.start_urls = ['http://www.example.com/categories/%s' % self.category]
# ...

And arguments are also received in spider constructors::

import scrapy

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