Парсинг JSON в Python. Как брать конкретные данные?

Question

[Лаврентий Федотов]

Есть json

{"result":{"stats":[{"profitability_above_ltc":"41.61","price":"0.0282","profitability_ltc":"0.0199","algo":0,"speed":"243.45559900"},{"price":"0.6757","profitability_btc":"0.5956","profitability_above_btc":"13.44","algo":1,"speed":"18171866.00000000"},{"profitability_above_ltc":"-100.00","price":"0.0000","profitability_ltc":"0.0199","algo":2,"speed":"0.00000000"},{"profitability_above_ltc":"567.12","price":"0.0089","profitability_ltc":"0.0199","algo":3,"speed":"563.12656201"},{"profitability_above_ltc":"148.13","price":"0.0076","profitability_ltc":"0.0199","algo":4,"speed":"0.13909400"},{"profitability_above_ltc":"1558.07","price":"0.0007","profitability_ltc":"0.0199","algo":5,"speed":"15.08137400"},{"profitability_above_ltc":"-37.04","price":"0.0025","profitability_ltc":"0.0199","algo":6,"speed":"0.94719039"},{"profitability_above_ltc":"1172.32","price":"0.0181","profitability_ltc":"0.0199","algo":7,"speed":"0.00532400"},{"profitability_above_ltc":"2211.17","price":"1.0237","profitability_ltc":"0.0199","algo":8,"speed":"0.02628506"},{"profitability_above_ltc":"982.62","price":"0.1233","profitability_ltc":"0.0199","algo":9,"speed":"0.61854782"},{"profitability_above_ltc":"-100.00","price":"0.0000","profitability_ltc":"0.0199","algo":10,"speed":"0.00000000"},{"profitability_above_ltc":"478.74","price":"0.0072","profitability_ltc":"0.0199","algo":11,"speed":"1.01352300"},{"profitability_above_ltc":"731.45","price":"0.0079","profitability_ltc":"0.0199","algo":12,"speed":"15.98064700"},{"profitability_above_ltc":"-100.00","price":"0.0000","profitability_ltc":"0.0199","algo":13,"speed":"0.00000000"},{"profitability_above_ltc":"3304.89","price":"0.0399","profitability_ltc":"0.0199","algo":14,"speed":"73.06248541"},{"profitability_above_ltc":"-100.00","price":"0.0000","profitability_ltc":"0.0199","algo":15,"speed":"0.00000000"},{"profitability_above_ltc":"3411.79","price":"0.0002","profitability_ltc":"0.0199","algo":16,"speed":"0.00000000"},{"profitability_above_ltc":"-100.00","price":"0.0000","profitability_ltc":"0.0199","algo":17,"speed":"0.00000000"},{"profitability_above_ltc":"879604.26","price":"0.0501","profitability_ltc":"0.0199","algo":18,"speed":"0.00000000"},{"profitability_above_ltc":"-100.00","price":"0.0002","profitability_ltc":"0.0199","algo":19,"speed":"0.00002661"},{"price":"0.0353","algo":20,"speed":"250.11615500","profitability_eth":"0.0303","profitability_above_eth":"16.42"},{"profitability_above_ltc":"3451536.43","price":"0.3621","profitability_ltc":"0.0199","algo":21,"speed":"1579.02181414"},{"profitability_above_ltc":"-100.00","price":"1.1503","profitability_ltc":"0.0199","algo":22,"speed":"0.00463899"},{"profitability_above_ltc":"-100.00","price":"4.1517","profitability_ltc":"0.0199","algo":23,"speed":"15.87700000"},{"profitability_above_ltc":"-100.00","price":"0.0030","profitability_ltc":"0.0199","algo":24,"speed":"0.00643681"},{"profitability_above_ltc":"-100.00","price":"1.2520","profitability_ltc":"0.0199","algo":25,"speed":"1104.98494638"}]},"method":"stats.global.current"}

Как парсить json я знаю, но как из этого кода брать конкретный price и speed для каждого algo?
Например, если мне нужна скорость и цена от 20 algo?

Если можно примером кода. Спасибо.

Answer 1

[Владимир Куц]

>>> import json
>>> a = json.loads('ваша строка')
>>> res = filter(lambda x: x['algo']==20, a['result']['stats'])
>>> res
[{u'profitability_above_eth': u'16.42', u'price': u'0.0353', u'speed': u'250.11615500', u'algo': 20, u'profitability_eth': u'0.0303'}]
>>> res[0]['algo']
20
>>> res[0]['speed']
u'250.11615500'
>>> res[0]['price']
u'0.0353'

Comments

[Лаврентий Федотов]

Приветствую. Возник вопрос: как при такой же задаче вытягивать данные из json в котором нет числовых значений? Т.е. тут фильтр идёт по algo, а если algo нет? А есть только буквенное значение?

{"market":"btce","market_name":"Btc-e.com","pair":"btc_usd","last":"1062","change_24":-3.19,"low_24":"1035.12","high_24":"1121.59","vol":"11004146.82"}

Как в данном случае фильтровать по pair в json?

[Владимир Куц]

res = filter(lambda x: x['pair']=='btc_usd', a['result']['stats'])
если вас правильно понял

[Лаврентий Федотов]

Да, поняли правильно, я тоже пытался так сделать, но получаю ошибку что list должен быть int, а не str

[Владимир Куц]

lavr_fedotov: ну во-первых - вашу структуру нужно десериализовать
a = json.loads('ваша строка'),
а потом уже работать над ней.
Во-вторых - ключ по которому вы собираетесь искать - я так понимаю - не обязательно присутствует в строке. Тогда немного дополните условие:
res = filter(lambda x: 'pair' in x.keys() and x['pair']=='btc_usd', a['result']['stats'])

[Лаврентий Федотов]

Понятно, спасибо. А если мне нужно искать ещё и по "market"? Возможно ли прописать в filter два условия?

res = filter(lambda x: 'pair' in x.keys() and x['market']=='btce', and x['pair']=='btc_usd', a['last'])
?

[Лаврентий Федотов]

url = 'https://cryptochan.org/graph/v3/stats.php'
jsonurl = urllib.urlopen(url)
a = json.loads(jsonurl.read())
res = filter(lambda x: x['market']=='btce' and x['pair']=='btc_usd', a['last'])

Всё равно выдаёт ошибку "list indices must be integers not str"

[Владимир Куц]

lavr_fedotov: у вас "a" уже в виде списка приходит
res = filter(lambda x: x['market']=='btce' and x['pair']=='btc_usd', a)

[Лаврентий Федотов]

Владимир Куц: Разобрался, огромное спасибо!