8

我试图弄清楚如何在 Python 中查询 JSON 数组。有人可以告诉我如何通过一个相当复杂的数组进行简单的搜索和打印吗？

我使用的例子在这里：http ://eu.battle.net/api/wow/realm/status

例如，我想看看如何找到“Silvermoon”服务器，并打印出它的“人口”，然后是“Wintergrasp”数组中的“控制派系”。

数组片段当前如下所示：

{"type":"pve","population":"high","queue":false,"wintergrasp":{"area":1,"controlling-faction":0,"status":0,"next":1382350068792},"tol-barad":{"area":21,"controlling-faction":0,"status":0,"next":1382349141932},"status":true,"name":"Silvermoon","slug":"silvermoon","battlegroup":"Cyclone / Wirbelsturm","locale":"en_GB","timezone":"Europe/Paris"}

目前我可以访问主数组，但如果不将整个内容复制到另一个似乎很浪费的新变量，似乎无法访问子数组。我希望能够做类似的事情

import urllib2
import json

req = urllib2.Request("http://eu.battle.net/api/wow/realm/status", None, {})
opener = urllib2.build_opener()
f = opener.open(req)

x = json.load(f)  # open the file and read into a variable

# search and find the Silvermoon server
silvermoon_array = ????

# print the population
print silvermoon_array.????

# access the Wintergrasp sub-array
wintergrasp_sub = ????
print wintergrasp_sub.????  # print the controlling-faction variable

这真的会帮助我掌握如何访问其他东西。

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3 回答 3

13

Python 的交互模式是逐步探索结构化数据的好方法。很容易找到如何访问，例如，silvermoon 服务器数据：

>>> data=json.load(urllib2.urlopen("http://eu.battle.net/api/wow/realm/status"))
>>> type(data)
<type 'dict'>
>>> data.keys()
[u'realms']
>>> type(data['realms'])
<type 'list'>
>>> type(data['realms'][0])
<type 'dict'>
>>> data['realms'][0].keys()
[u'status', u'wintergrasp', u'battlegroup', u'name', u'tol-barad', u'locale', u'queue', u'timezone', u'type', u'slug', u'population']
>>> data['realms'][0]['name']
u'Aegwynn'
>>> [realm['name'] for realm in data['realms']].index('Silvermoon')
212
>>> silvermoon= data['realms'][212]
>>> silvermoon['population']
u'high'
>>> type(silvermoon['wintergrasp'])
<type 'dict'>
>>> silvermoon['wintergrasp'].keys()
[u'status', u'next', u'controlling-faction', u'area']
>>> silvermoon['wintergrasp']['controlling-faction']
>>> silvermoon['population']
u'high'

如果您还不了解它们，您应该阅读dictionary.keys、list.index和列表推导以了解发生了什么。

在弄清楚数据的结构之后，您终于可以将数据访问重写为更具可读性和效率：

realms= data['realms']
realm_from_name= dict( [(realm['name'], realm) for realm in realms])
print realm_from_name['Silvermoon']['population']
print realm_from_name['Silvermoon']['wintergrasp']['controlling-faction']

至于将数组复制到另一个变量是浪费的，您应该知道python通过引用传递值。这意味着当您将某些内容分配给新变量时，不涉及复制。以下是按值传递与按引用传递的简单解释

最后，您似乎过度担心性能。Python 的理念是先做好，后优化。当你让它正常工作并且如果你需要更好的性能，优化它，如果它值得花时间。

于 2013-10-21T10:14:37.550 回答
1

这可以满足您的要求：

# -*- coding: utf-8 -*-
import json
import urllib2

def searchListOfDicts(listOfDicts, attr, value):
    """
    Loops through a list of dictionaries and returns matching attribute value pair
    You can also pass it slug, silvermoon or type, pve
    returns a list containing all matching dictionaries 
    """
    matches = [record for record in listOfDicts if attr in record and record[attr] == value]
    return matches

def myjsonDict():
    """
    Opens url, grabs json and puts it inside a dictionary
    """
    req = urllib2.Request("http://eu.battle.net/api/wow/realm/status", None, {})
    opener = urllib2.build_opener()
    f = opener.open(req)
    json_dict = json.load(f)
    return json_dict

jsonDict = myjsonDict()
#we want to search inside realms list
silverMoonServers = searchListOfDicts(jsonDict["realms"], "name", "Silvermoon")
#access first dictionary that matched "name, Silvermoon" query
print silverMoonServers[0]
print silverMoonServers[0]["wintergrasp"]
print silverMoonServers[0]["wintergrasp"]["controlling-faction"]
于 2013-10-21T10:05:49.800 回答
0

在 Python 中，json.loads将 json 对象映射到 python 字典，然后映射Arrays到list，因此进一步的操作就像使用常规的 pythondict和list结构一样。

以下是如何使用请求和lamdbas：

    import json
    import requests

    response = requests.get("http://eu.battle.net/api/wow/realm/status")
    json_data = json.loads(response.text)

    # loop through the list of realms to find the one you need (realm_name)
    get_realm = lambda realm_name, jd: [r for r in jd['realms'] 
                                        if r['name'] == realm_name]

    # extract data you need, if there is a match in the list of realms,
    # return None otherwise
    get_your_data = lambda realm: (
        realm[0]['name'],
        realm[0]['wintergrasp']['controlling-faction']
    ) if realm else None

    print get_your_data(get_realm('Silvermoon', json_data))
于 2013-10-21T09:48:52.440 回答