用于过滤 JSON 对象中包含特定值的数组的 Python 脚本

Question

我有一个 json 对象，它由一个带有键“data”的对象组成，该对象的值列在一组数组中。我需要返回包含值 x 的所有数组，但数组本身没有键。我正在尝试编写一个脚本来输入源文件(inFile)并定义导出文件(outFile)。这是我的数据结构:

{ "data": [
       ["x", 1, 4, 6, 2, 7],
       ["y", 3, 2, 5, 8, 4],
       ["z", 5, 2, 5, 9, 9],
       ["x", 3, 7, 2, 6, 8]
     ]
}

这是我当前的脚本:

import json

def jsonFilter( inFile, outFile ):
    out = None;

    with open( inFile, 'r') as jsonFile:
       d = json.loads(json_data)
       a = d['data']
       b = [b for b in a if b != 'x' ]
       del b
       out = a


    if out:
        with open( outFile, 'w' ) as jsonFile:
            jsonFile.write( json.dumps( out ) );

    else:
       print "Error creating new jsonFile!"

解决方案

感谢 Rob 和大家的帮助!这是最终的工作命令行工具。这需要两个参数:inFile 和 Outfile。 ~$ python jsonFilter.py inFile.json outFile.json

import json

def jsonFilter( inFile, outFile ):
    # make a dictionary.
    out = {};

    with open( inFile, 'r') as jsonFile:
       json_data = jsonFile.read()
       d = json.loads(json_data)
       # build the data you want to save to look like the original
       # by taking the data in the d['data'] element filtering what you want
       # elements where b[0] is 'x'
       out['data'] = [b for b in d['data'] if b[0] == 'x' ]


    if out:
        with open( outFile, 'w' ) as jsonFile:
            jsonFile.write( json.dumps( out ) );

    else:
       print "Error creating new JSON file!"

if __name__ == "__main__":
     import argparse

     parser = argparse.ArgumentParser()
     parser.add_argument('inFile', nargs=1, help="Choose the in file to use")
     parser.add_argument('outFile', nargs=1, help="Choose the out file to use")
     args = parser.parse_args()
     jsonFilter( args.inFile[0] , args.outFile[0] );

Answer 1

第一个问题，查询字符串对于所有内容都是正确的(也称为返回整个数据集，因为您正在将 b(列表)与“x”字符串进行比较

  b = [b for b in a if b != 'x' ]

你想做的是:

  b = [b for b in a if b[0] != 'x' ]

第二个问题是您试图通过查询和删除结果来删除数据。由于结果包含一个副本，不会从原始容器中删除任何内容。
相反，仅使用您想要的元素构建新数据，然后保存它们。此外，您没有在输出数据中重新创建“data”元素，因此输出的 json 具有与输入数据相同的结构。

import json

def jsonFilter( inFile, outFile ):
    # make a dictionary instead.
    out = {};

    with open( inFile, 'r') as jsonFile:
       json_data = jsonFile.read()
       d = json.loads(json_data)
       # build the data you want to save to look like the original
       # by taking the data in the d['data'] element filtering what you want
       # elements where b[0] is 'x'
       out['data'] = [b for b in d['data'] if b[0] == 'x' ]


    if out:
        with open( outFile, 'w' ) as jsonFile:
            jsonFile.write( json.dumps( out ) );

    else:
       print "Error creating new jsonFile!"

输出 json 数据如下所示:

 '{"data": [["x", 1, 4, 6, 2, 7], ["x", 3, 7, 2, 6, 8]]}'

如果您不希望输出包含“data”根元素，而只是包含与过滤器匹配的数据数组，则更改该行:

 out['data'] = [b for b in d['data'] if b[0] == 'x' ]

到

 out = [b for b in d['data'] if b[0] == 'x' ]

经过此更改，输出 json 数据如下所示:

 '[["x", 1, 4, 6, 2, 7], ["x", 3, 7, 2, 6, 8]]'