All the Places
A project to extract GeoJSON from the web focusing on websites that have 'store locator' pages like restaurants, gas stations, retailers, etc. Each chain has its own bit of software to extract useful information from their site (a "spider"). Each spider can be individually configured to throttle request rate to act as a good citizen on the Internet. The default
User-Agent for the spiders can be found here, so websites wishing to prevent our spiders from accessing the data on their website can block that User Agent.
The project is built using
scrapy, a Python-based web scraping framework. Each target website gets its own spider, which does the work of extracting interesting details about locations and outputting results in a useful format.
Adding a spider
To scrape a new website for locations, you'll want to create a new spider. You can copy from existing spiders or start from a blank, but the result is always a Python class that has a
process() function that
GeojsonPointItems. The Scrapy framework does the work of outputting the GeoJSON based on these objects that the spider generates.
To get started, you'll want to install the dependencies for this project.
This project uses
pipenvto handle dependencies and virtual environments. To get started, make sure you have
pipenvinstalled, make sure you have the
all-the-placesrepository checked out
git clone firstname.lastname@example.org:alltheplaces/alltheplaces.git
Then you can install the dependencies for the project
cd alltheplaces pipenv install
After dependencies are installed, make sure you can run the
scrapycommand without error
pipenv run scrapy
pipenv run scrapyran without complaining, then you have a functional
scrapysetup and are ready to write a scraper.
Create a new spider
Create a new file in
locations/spiders/with this content:
# -*- coding: utf-8 -*- import scrapy from locations.items import GeojsonPointItem class TemplateSpider(scrapy.Spider): name = "template" allowed_domains = ["www.sample.com"] start_urls = ( 'https://www.sample.com/locations/', ) def parse(self, response): pass
This blank/template spider will start at the given
start_urls, only touch the domains listed in
allowed_domains, and all web requests will be returned to the
parse()function with response content in the
responseargument. Once you have the response content, you can perform various operations on it. For example, the most useful is probably running XPath selections on the HTML of the page to extract data out of the page. Check out the "Scraper tips" section below for more information about how to use these tools to efficiently get data out of the page.
Once you have your spider written, you can give it a test run to make sure it's finding the expected results.
pipenv run scrapy crawl template
scrapy crawl templatecommand runs a spider named
template. If you changed the name of your spider, you should use the name you chose. By default,
scrapy crawldoes not save the output anywhere, but it does log the results of the spider operation fairly verbosely.
To generate GeoJSON locally, you can enable a couple options during the crawl process to use the GeoJSON exporter and to specify the file to write it to:
pipenv run scrapy crawl template \ --output-format=geojson \ --output=output.geojson
Finally, make sure your
GeojsonPointItems that contain the location and property data that you extract from the page:
def parse(self, response): yield GeojsonPointItem( lat=latitude, lon=longitude, addr_full="1234 Fifth Street", city="San Francisco", state="CA" )
Once you have a spider that logs out useful results, you can create a new branch and push it up to your fork to create a pull request. The build system will run your spider and output information about the results as a comment on your pull request.
Tips for writing a spider
Prefer a directory of all locations
Most listings of locations come in two flavors: a "store finder" that lets the user search by location and a "store directory" that is a hierarchical listing of all locations. These listings are sometimes hidden in the footer or on the site map page. Keep an eye out for these, because it's a lot easier if they enumerate all the locations for you rather than having to program a spider to do it for you.
If the only option is search by location, there is likely an AJAX query made to search by latitude/longitude. Keep an eye on your browser's developer tools "network" tab to see what the request is so you can replicate it in your spider.
You can send the spider to other pages
The simplest thing a spider can do is to load the
start_urls, process the page, and
yield the data as
GeojsonPointItem objects from the
parse() method. Usually that's not enough to get at useful data, though. The
parse() method can also
yield a Request object, which scrapy will use to add another URL to the request queue.
By default, the
parse() method on the spider will be called with the response for the new request. In many cases it's easier to create a new function to parse the new page's content and pass that function in via the
callback parameter like so:
yield scrapy.Request( response.urljoin(store_url.extract()), callback=self.parse_store )
Since the next URL you want to request is usually pulled from an
href in the page and relative to the page you're on, you can use the
response.urljoin() method as a shortcut to build the URL for the next request.
Using the scrapy shell
Instead of running the
scrapy crawl every time you want to try your spider, you can use the Scrapy shell to load a page and experiment with XPath queries. Once you're happy with the query that extracts interesting data you can use it in your spider. This is a whole lot easier than running the whole crawl command every time you make a change to your spider.
To enter the shell, use
scrapy shell http://example.com (where you replace the URL with your own). It will dump you into a Python shell after having requested the page and parsing it. Once in the shell, you can do things with the
response object as if you were in your spider. The shell also offers a shortcut function called
fetch() that lets you pull up a different page.