Python Forum

HI,
I am trying to understand how the module python-craigslist works.
The __init__.py file is too long to be posted here, so I cut a simplified version to give an idea.

from six import iteritems


class CraigslistBase(object):
    """ Base class for all Craiglist wrappers. """

    base_filters = {
        'query': {'url_key': 'query', 'value': None},
        'search_titles': {'url_key': 'srchType', 'value': 'T'},
        'has_image': {'url_key': 'hasPic', 'value': 1},
        'posted_today': {'url_key': 'postedToday', 'value': 1},
        'search_distance': {'url_key': 'search_distance', 'value': None},
        'zip_code': {'url_key': 'postal', 'value': None},
    }
    extra_filters = {}

    def __init__(self, filters=None):

        self.filters = {}
        for key, value in iteritems((filters or {})):
            filter = (self.base_filters.get(key) or
                      self.extra_filters.get(key))
            if filter['value'] is None:
                self.filters[filter['url_key']] = value
            elif isinstance(filter['value'], list):
                valid_options = filter['value']
                if not hasattr(value, '__iter__'):
                    value = [value]  # Force to list
                options = []
                for opt in value:
                        options.append(valid_options.index(opt) + 1)

                self.filters[filter['url_key']] = options
            elif value:  # Don't add filter if ...=False
                self.filters[filter['url_key']] = filter['value']


class CraigslistHousing(CraigslistBase):
    """ Craigslist housing wrapper. """

    default_category = 'hhh'
    custom_result_fields = True

    extra_filters = {
        'private_room': {'url_key': 'private_room', 'value': 1},
        'private_bath': {'url_key': 'private_bath', 'value': 1},
        'cats_ok': {'url_key': 'pets_cat', 'value': 1},
        'dogs_ok': {'url_key': 'pets_dog', 'value': 1},
        'min_price': {'url_key': 'min_price', 'value': None},
        'max_price': {'url_key': 'max_price', 'value': None},
        'min_ft2': {'url_key': 'minSqft', 'value': None},
        'max_ft2': {'url_key': 'maxSqft', 'value': None},
        'min_bedrooms': {'url_key': 'min_bedrooms', 'value': None},
        'max_bedrooms': {'url_key': 'max_bedrooms', 'value': None},
        'min_bathrooms': {'url_key': 'min_bathrooms', 'value': None},
        'max_bathrooms': {'url_key': 'max_bathrooms', 'value': None},
        'no_smoking': {'url_key': 'no_smoking', 'value': 1},
        'is_furnished': {'url_key': 'is_furnished', 'value': 1},
        'wheelchair_acccess': {'url_key': 'wheelchaccess', 'value': 1},
    }

The code is run as following:

ch_l = CraigslistHousing(filters={'max_price': 1200,
                                  'private_room': True})
print(ch_l.filters)

I am interested in what happens in line 28. As I understand, we pass "filters" as a dictionary through the sub-class CraigslistHousing. I'd assume the code would loop through that but, before the loop, the code sets

filters = {}

As far as I understand, this overrides what we passed as a parameter to the function but clearly that is not the case.
Can anyone explain it to me?
Thank you

PS: Here's the link to the original module, with the full functioning code.

you need to make difference between filters that is passed as argument when instantiate the object and self.filters which is filters attribute of the [instance of] the class.
On line 28 it sets self.filters to be empty dict and then it iterates over items in the filters that you pass when create/init the class instance and populates the self.filters. The reason - it that does need some preprocessing of the filters argument key/values

Sure, I didn't notice they were two different variables!
Thank you