rentswatch-scraper 1.0.1

Description:

rentswatchscraper 1.0.1

This package provides an easy and maintenable way to build a
Rentswatch scraper. Rentswatch is a cross-borders investigation that collects data on flat rents in Europe. Its scrapers mainly focus on classified ads.

How to install
Install using pip…
pip install rentswatch-scraper


How to use
Let’s take a look at a quick example of using Rentswatch Scraper to
build a simple model-backed scraper to collect data from a website.
First, import the package components to build your scraper:
#!/usr/bin/env python
from rentswatch_scraper.scraper import Scraper
from rentswatch_scraper.browser import geocode, convert
from rentswatch_scraper.fields import RegexField, ComputedField
from rentswatch_scraper import reporting
To factorize as much code as possible we created an abstract class that
every scraper will implement. For the sake of simplicity we’ll use a
dummy website as follow:
class DummyScraper(Scraper):
# Those are the basic meta-properties that define the scraper behavior
class Meta:
country = 'FR'
site = "dummy"
baseUrl = 'http://dummy.io'
listUrl = baseUrl + '/rent/city/paris/list.php'
adBlockSelector = '.ad-page-link'
Without any further configuration, this scraper will start to collect
ads from the list page of dummy.io. To find links to the ads, it
will use the CSS selector .ad-page-link to get <a> markups and
follow their href attributes.
We have now to teach the scraper how to extract key figures from the ad
page.
class DummyScraper(Scraper):
# HEADS UP: Meta declarations are hidden here
# ...
# ...

# Extract data using a CSS Selector.
realtorName = RegexField('.realtor-title')
# Extract data using a CSS Selector and a Regex.
serviceCharge = RegexField('.description-list', 'charges : (.*)\s€')
# Extract data using a CSS Selector and a Regex.
# This will throw a custom exception if the field is missing.
livingSpace = RegexField('.description-list', 'surface :(\d*)', required=True, exception=reporting.SpaceMissingError)
# Extract the value directly, without using a Regex
totalRent = RegexField('.description-price', required=True, exception=reporting.RentMissingError)
# Store this value as a private property (begining with a underscore).
# It won't be saved in the database but it can be helpful as you we'll see.
_address = RegexField('.description-address')
Every attribute will be saved as an Ad’s property, according to the Ad
model.
Some properties may not be extractable from the HTML. You may need to
use a custom function that received existing properties. For this reason
we created a second field type named ComputedField. Since the
properties order of declaration is recorded, we can use previously
declared (and extracted) values to compute new ones.
class DummyScraper(Scraper):
# ...
# ...

# Use existing properties `totalRent` and `livingSpace` as they were
# extracted before this one.
pricePerSqm = ComputedField(fn=lambda s, values: values["totalRent"] / values["livingSpace"])
# This full exemple uses private properties to find latitude and longitude.
# To do so we use a buid-in function named `convert` that transforms an
# address into a dictionary of coordinates.
_latLng = ComputedField(fn=lambda s, values: geocode(values['_address'], 'FRA') )
# Gets a the dictionary field we want.
latitude = ComputedField(fn=lambda s, values: values['_latLng']['lat'])
longitude = ComputedField(fn=lambda s, values: values['_latLng']['lng'])
All you need to do now is to create an instance of your class and run
the scraper.
# When you script is executed directly
if __name__ == "__main__":
dummyScraper = DummyScraper()
dummyScraper.run()


API Doc

class Ad
Attributes
As seen above, every Ad attribute might be used as a Scraper attribute to declare which attribute extract.


Name
Type
Description



status
String
“listed” if needs more scraping, “scraped” if it’s done

site
String
Name of the website

createdAt
DateTime
Date the ad was first scraped

siteId
String
The unique ID from the site where it’s scrapped from

serviceCharge
Float
Extra costs (heating mostly)

baseRent
Float
Base costs (without heating)

totalRent
Float
Total cost

livingSpace
Float
Surface in square meters

pricePerSqm
Float
Price per square meter

furnished
Bool
True if the flat or house is furnished

realtor
Bool
True if realtor, n if rented by a physical person

realtorName
Unicode
The name of the realtor or person offering the flat

latitude
Float
Latitude

longitude
Float
Longitude

balcony
Bool
True if there is a balcony/terrasse

yearConstructed
String
The year the building was built

cellar
Bool
True if the flat comes with a cellar

parking
Bool
True if the flat comes with a parking or a garage

houseNumber
String
House Number in the street

street
String
Street name (incl. “street”)

zipCode
String
ZIP code

city
Unicode
City

lift
Bool
True if a lift is present

typeOfFlat
String
Type of flat (no typology)

noRooms
String
Number of rooms

floor
String
Floor the flat is at

garden
Bool
True if there is a garden

barrierFree
Bool
True if the flat is wheelchair accessible

country
String
Country, 2 letter code

sourceUrl
String
URL of the page





class Scraper
Methods
The Scraper class defines a lot of method that we encourage you to
redefine in order to have the full control of your scraper behavior.


Name
Description



extract_ad
Extract ads list from a page’s soup.

fail
Print out an error message.

fetch_ad
Fetch a single ad page from the target website then create Ad instances by calling èxtract_ad.

fetch_series
Fetch a single list page from the target website then fetch an ad by calling fetch_ad.

find_ad_blocks
Extract ad block from a page list. Called within fetch_series.

get_ad_href
Extract a href attribute from an ad block. Called within fetch_series.

get_ad_id
Extract a siteId from an ad block. Called within fetch_series.

get_fields
Used internally to generate a list of property to extract from the ad.

get_series
Fetch a list page from the target website.

has_issue
True if we met issues with this ad before.

is_scraped
True if we already scraped this ad before.

ok
Print out an success message.

prepare
Just before saving the values.

run
Run the scrapper.

transform_page
Transform HTML content of the series page before parsing it.






Start a migration
Use Yoyo:
yoyo new ./migrations -m "Your migration's description"
And apply it:
yoyo apply --database mysql://user:password@host/db ./migrations