生成动态嵌套 JSON 对象和数组 - python

Question

正如问题所解释的那样，我一直在尝试生成嵌套的 JSON 对象。在这种情况下，我有 for 循环从字典 dic 中获取数据。下面是代码：

f = open("test_json.txt", 'w')
flag = False
temp = ""
start = "{\n\t\"filename\"" + " : \"" +initial_filename+"\",\n\t\"data\"" +" : " +" [\n"
end = "\n\t]" +"\n}"
f.write(start)
for i, (key,value) in enumerate(dic.iteritems()):
    f.write("{\n\t\"keyword\":"+"\""+str(key)+"\""+",\n")
    f.write("\"term_freq\":"+str(len(value))+",\n")
    f.write("\"lists\":[\n\t")
    for item in value:
        f.write("{\n")
        f.write("\t\t\"occurance\" :"+str(item)+"\n")
        #Check last object
        if value.index(item)+1 == len(value):
            f.write("}\n" 
            f.write("]\n")
        else:
            f.write("},") # close occurrence object
    # Check last item in dic
    if i == len(dic)-1:
        flag = True
    if(flag):
        f.write("}")
    else:
        f.write("},") #close lists object
        flag = False 

#check for flag
f.write("]") #close lists array 
f.write("}")

预期输出为：

{
"filename": "abc.pdf",
"data": [{
    "keyword": "irritation",
    "term_freq": 5,
    "lists": [{
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 2
    }]
}, {
    "keyword": "bomber",
    "lists": [{
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 2
    }],
    "term_freq": 5
}]
}

但目前我得到如下输出：

{
"filename": "abc.pdf",
"data": [{
    "keyword": "irritation",
    "term_freq": 5,
    "lists": [{
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 2
    },]                // Here lies the problem "," before array(last element)
}, {
    "keyword": "bomber",
    "lists": [{
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 1
    }, {
        "occurance": 2
    },],                  // Here lies the problem "," before array(last element)
    "term_freq": 5
}]
}

请帮忙，我试图解决它，但失败了。请不要将其标记为重复，因为我已经检查了其他答案并且根本没有帮助。

编辑 1： 输入基本上取自映射类型为 <String, List> 的字典 dic 例如："irritation" => [1,3,5,7,8] 其中刺激是关键，并映射到页码列表。这基本上是在外部 for 循环中读取的，其中键是关键字，值是该关键字出现的页面列表。

编辑 2：

dic = collections.defaultdict(list) # declaring the variable dictionary
dic[key].append(value) # inserting the values - useless to tell here
for key in dic:
    # Here dic[x] represents list - each value of x
    print key,":",dic[x],"\n" #prints the data in dictionary

Answer 1

您当前的代码无法正常工作，因为循环遍历 before-last 项并添加 }, 然后当循环再次运行时它会将标志设置为 false，但最后一次运行它添加了一个 , 因为它认为还会有另一个元素。

如果这是你的命令：a = {"bomber":[1,2,3,4,5]} 那么你可以这样做：

import json
file_name = "a_file.json"
file_name_input = "abc.pdf"
new_output = {}
new_output["filename"] = file_name_input

new_data = []
i = 0
for key, val in a.iteritems():
   new_data.append({"keyword":key, "lists":[], "term_freq":len(val)})
   for p in val:
       new_data[i]["lists"].append({"occurrance":p})
   i += 1

new_output['data'] = new_data

然后通过以下方式保存数据：

f = open(file_name, 'w+')
f.write(json.dumps(new_output, indent=4, sort_keys=True, default=unicode))
f.close()

Answer 2

什么@andrea-f我觉得不错，这里是另一个解决方案：

请随意选择两者:)

import json

dic = {
        "bomber": [1, 2, 3, 4, 5],
        "irritation": [1, 3, 5, 7, 8]
      }

filename = "abc.pdf"

json_dict = {}
data = []

for k, v in dic.iteritems():
  tmp_dict = {}
  tmp_dict["keyword"] = k
  tmp_dict["term_freq"] = len(v)
  tmp_dict["lists"] = [{"occurrance": i} for i in v]
  data.append(tmp_dict)

json_dict["filename"] = filename
json_dict["data"] = data

with open("abc.json", "w") as outfile:
    json.dump(json_dict, outfile, indent=4, sort_keys=True)

同样的思路，我先创建一个大的json_dict直接保存在json中。我使用 with 语句来保存 json 避免捕获 exception

此外，如果您需要进一步改进 json 输出，您应该查看 json.dumps() 的文档。

编辑

只是为了好玩，如果你不喜欢 tmp var，你可以在 one-liner 中循环所有数据 for :)

json_dict["data"] = [{"keyword": k, "term_freq": len(v), "lists": [{"occurrance": i} for i in v]} for k, v in dic.iteritems()]

它可以为最终解决方案提供一些不完全可读的内容，如下所示：

import json

json_dict = {
              "filename": "abc.pdf",
              "data": [{
                        "keyword": k,
                        "term_freq": len(v),
                        "lists": [{"occurrance": i} for i in v]
                       } for k, v in dic.iteritems()]
            }

with open("abc.json", "w") as outfile:
    json.dump(json_dict, outfile, indent=4, sort_keys=True)

编辑 2

您似乎不想将 json 保存为所需的输出，但可以阅读它。

其实你也可以使用json.dumps()来打印你的json.

with open('abc.json', 'r') as handle:
    new_json_dict = json.load(handle)
    print json.dumps(json_dict, indent=4, sort_keys=True)

这里还有一个问题，"filename": 打印在列表的末尾，因为 data 的 d 在 f 之前。

要强制执行命令，您必须在生成字典时使用 OrderedDict。小心 python 2.X

的语法很难看（imo）

这是新的完整解决方案 ;)

import json
from collections import OrderedDict

dic = {
        'bomber': [1, 2, 3, 4, 5],
        'irritation': [1, 3, 5, 7, 8]
      }

json_dict = OrderedDict([
              ('filename', 'abc.pdf'),
              ('data', [ OrderedDict([
                                        ('keyword', k),
                                        ('term_freq', len(v)),
                                        ('lists', [{'occurrance': i} for i in v])
                                     ]) for k, v in dic.iteritems()])
            ])

with open('abc.json', 'w') as outfile:
    json.dump(json_dict, outfile)


# Now to read the orderer json file

with open('abc.json', 'r') as handle:
    new_json_dict = json.load(handle, object_pairs_hook=OrderedDict)
    print json.dumps(json_dict, indent=4)

将输出：

{
    "filename": "abc.pdf", 
    "data": [
        {
            "keyword": "bomber", 
            "term_freq": 5, 
            "lists": [
                {
                    "occurrance": 1
                }, 
                {
                    "occurrance": 2
                }, 
                {
                    "occurrance": 3
                }, 
                {
                    "occurrance": 4
                }, 
                {
                    "occurrance": 5
                }
            ]
        }, 
        {
            "keyword": "irritation", 
            "term_freq": 5, 
            "lists": [
                {
                    "occurrance": 1
                }, 
                {
                    "occurrance": 3
                }, 
                {
                    "occurrance": 5
                }, 
                {
                    "occurrance": 7
                }, 
                {
                    "occurrance": 8
                }
            ]
        }
    ]
}

但要小心，大多数时候，最好保存一个常规 .json 文件以便跨语言。

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