Question

我想为json.loads中不存在的密钥添加默认值

我有这样的键列表

["id", "name", "wkt", "created", "radius", "round"]

和许多行json文件，它们没有这样的键：

{"id":"1", "name":"a", "round":5}   
{"id":"2", "wkt": "POINT(1.1)", "created":"2018-22-11T10:00:00"}   
{"id":"3", "radius":3}

预期结果：

{"id":"1", "name": "a", "wkt":null, "created":null, "radius":null, "round":5}

我当前的解决方案

for line in lines:
    line_dict = json.loads(line)
    for key in keys:
        if not key in line_dict:
            line_dict[key] = None
    yield line_dict

期望结果

我想找到一种更有效的方法来为json.loads中不存在的键设置默认值。到目前为止，使用object_hooks或object_pair_hook都没有成功。

Answer 1

您可以初始化一个空值字典并进行相应的更新。

keys = ["id", "name", "wkt", "created", "radius", "round"]       
default = dict.fromkeys(keys, None)

def read_json(filename):
    with open(filename, 'r') as f: 
        for line in f:
            d = default.copy()
            d.update(json.loads(line))
            yield d

Answer 2

我可能会误解您的问题，但是您不能这样做吗？

def filler(d):
   for i in ["id", "name", "wkt", "created", "radius", "round"]:
     if i not in d:
       d[i] = None
   return d

json.loads('{"id":"1", "name":"a", "round":5}', object_hook=filler)

对我来说，这返回

{u'name': u'a', 'created': None, u'id': u'1', 'radius': None, 'wkt': None, u'round': 5}

从json.loads设置字典的默认值

2 个答案: