用Python中的字典循环遍历字典列表的正确方法

Question

I have an list of vehicles and a dict of filters. The code is as follows:

The dictionary of filters is as follows:

filters = {
  'make': 'SKODA',
  'model': 'Fabia',
  'fuel': 'Diesel',
  'transmission': '',
  'registration_year': '',
  'price': {'start': 10000, 'stop': 12000}
}

And the list of vehicles is as follows:

vehicles = [
  {'make': 'AUDI', 'model': 'Q2 Dsl', 'type': '1.6 TDi Sport', 'fuel': 'Diesel', 'mileage': '19896', 'registration_year': '2017', 'transmission': 'Handbediende versnellingsbak', 'price': 17800}, 
  {'make': 'AUDI', 'model': 'A6 SW Dsl', 'type': '2.0 TDi S line', 'fuel': 'Diesel', 'mileage': '87354', 'registration_year': '2013', 'transmission': 'Handbediende versnellingsbak', 'price': 52000},
  {'make': 'SKODA', 'model': 'Fabia', 'type': '1.6 CR TDi GreenLine Active DPF', 'fuel': 'Diesel', 'mileage': '90613', 'registration_year': '2012', 'transmission': 'Handbediende versnellingsbak', 'price': 11000},
  {'make': 'AUDI', 'model': 'A4 SW Dsl', 'type': '2.0 TDi S tronic', 'fuel': 'Diesel', 'mileage': '47402', 'registration_year': '2016', 'transmission': 'Sequentiele bak', 'price': 93000},
  {'make': 'VOLKSWAGEN', 'model': 'Touran', 'type': '1.4 TSI Trendline', 'fuel': 'Essence', 'mileage': '28588', 'registration_year': '2017', 'transmission': 'Handbediende versnellingsbak', 'price': 87000},
  {'make': 'AUDI', 'model': 'A4 Dsl', 'type': '2.0 TDi', 'fuel': 'Diesel', 'mileage': '66053', 'registration_year': '2014', 'transmission': 'Handbediende versnellingsbak', 'price': 62000}
]

Thus, I want to loop through all vehicles and all filters and get back only those vehicles that match the filters. In this case I should get only Skoda .

I tried with pydash library, but without success.

What have I tried is as follows:

def filter_item(vehicle):
  vehicles = []
  for key, value in filters.items():
    if key == "price":
      if vehicle[key] > value['start'] and vehicle[key] < value['stop']:
        vehicles.append(vehicle)
    else:
      if vehicle[key] == value:
        vehicles.append(vehicle)
  return vehicles

result = py_.filter(vehicles, lambda x: filter_item(x))

But in this case I get all vehicles with fuel type Diesel , but I should get only the second one if we start from 0, thus only Skoda.

Any idea how can I do that? And is there a better way or cleaner code to do it?

Answer 1

you need to check agaist all filter conditions, here is an example with python builtin filter :

def filter_item(vehicle):
    vehicles = []
    for key, value in filters.items():
        if not value: # skip empty filter
            continue
        if key == "price":
            if vehicle[key] > value['start'] and vehicle[key] < value['stop']:
                continue
        else:
            if vehicle[key] == value:
                continue
        return False # no filter matched
    return True


result = filter(filter_item, vehicles)

with pydash:

result = py_.filter(vehicles, filter_item)

note: callback function passed to fitler returns true, to indicates the current value should include in the result.

Answer 2

I think the price range should be split off from filters . It's awkward in there because it's the only key that you can't directly match with the corresponding values for the same key of a vehicle.

I'd write it like this

>>> filters = {
...:  'make': 'SKODA',
...:  'model': 'Fabia',
...:  'fuel': 'Diesel',
...:  'transmission': '',
...:  'registration_year': '',
...:}
>>> price_range = range(10000, 12000 + 1)
>>>
>>> [vehicle['make'] for vehicle in vehicles if
...:all(vehicle.get(k) == v for k, v in filters.items() if v) and
...:vehicle['price'] in price_range]
>>> ['SKODA']

or like this

>>> [vehicle for vehicle in vehicles if
...:all(vehicle.get(k) == v for k, v in filters.items() if v) and
...:vehicle['price'] in price_range]
>>> 
[{'fuel': 'Diesel',
  'make': 'SKODA',
  'mileage': '90613',
  'model': 'Fabia',
  'price': 11000,
  'registration_year': '2012',
  'transmission': 'Handbediende versnellingsbak',
  'type': '1.6 CR TDi GreenLine Active DPF'}]

in case you want the full vehicle-dictionaries that match.