从JSON序列化中排除空/空值

Question

我使用带有simplejson的Python将多个嵌套字典序列化为JSON.

有没有办法自动排除空/空值？

例如,序列化:

 {
     "dict1" : {
     "key1" : "value1",
     "key2" : None
     }
 }

至

 {
     "dict1" : {
     "key1" : "value1"
     }
 }

使用Jackson和Java时,您可以使用它Inclusion.NON_NULL来执行此操作.有一个简单的json等价物吗？

Answer 1

def del_none(d):
    """
    Delete keys with the value ``None`` in a dictionary, recursively.

    This alters the input so you may wish to ``copy`` the dict first.
    """
    # For Python 3, write `list(d.items())`; `d.items()` won’t work
    # For Python 2, write `d.items()`; `d.iteritems()` won’t work
    for key, value in list(d.items()):
        if value is None:
            del d[key]
        elif isinstance(value, dict):
            del_none(value)
    return d  # For convenience

样品用法:

>>> mydict = {'dict1': {'key1': 'value1', 'key2': None}}
>>> print(del_none(mydict.copy()))
{'dict1': {'key1': 'value1'}}

然后你可以喂它json.

Answer 2

>>> def cleandict(d):
...     if not isinstance(d, dict):
...         return d
...     return dict((k,cleandict(v)) for k,v in d.iteritems() if v is not None)
... 
>>> mydict = dict(dict1=dict(key1='value1', key2=None))
>>> print cleandict(mydict)
{'dict1': {'key1': 'value1'}}
>>> 

我不喜欢del一般使用,更改现有字典可能会产生微妙的效果,具体取决于它们的创建方式.使用None删除创建新词典可以防止所有副作用.

Answer 3

我的 Python3 版本的好处是不改变输入，以及递归到嵌套在列表中的字典：

def clean_nones(value):
    """
    Recursively remove all None values from dictionaries and lists, and returns
    the result as a new dictionary or list.
    """
    if isinstance(value, list):
        return [clean_nones(x) for x in value if x is not None]
    elif isinstance(value, dict):
        return {
            key: clean_nones(val)
            for key, val in value.items()
            if val is not None
        }
    else:
        return value

例如：

a = {
    "a": None,
    "b": "notNone",
    "c": ["hello", None, "goodbye"],
    "d": [
        {
            "a": "notNone",
            "b": None,
            "c": ["hello", None, "goodbye"],
        },
        {
            "a": "notNone",
            "b": None,
            "c": ["hello", None, "goodbye"],
        }
    ]
}


print(clean_nones(a))

结果如下：

{
    'b': 'notNone',
    'c': ['hello', 'goodbye'],
    'd': [
        {
            'a': 'notNone',
            'c': ['hello', 'goodbye']
        },
        {
            'a': 'notNone',
            'c': ['hello', 'goodbye']
        }
    ]
}