JSON：每行保存一个字典

Question

如何将python字典列表保存到文件中，每个字典dict将保存在一行中？我知道我可以json.dump用来保存字典列表。但是我只能将列表以紧凑形式保存（一行中的完整列表）或缩进形式，其中为所有字典键添加一个换行符。

编辑：

我希望我的最终json文件如下所示：

[{key1:value,key2:value},
{key1:value,key2:value},
...
{key1:value,key2:value}]

Answer 1

我同意另一种回应-最好的办法是json.dump每个dict人都单独写一个逗号和换行符。这是我的处理方式：

import json

data = [
    {"key01":"value","key02":"value"},
    {"key11":"value","key12":"value"},
    {"key21":"value","key22":"value"}
]

import json
with open('file.json', 'w') as fp:
    fp.write(
        '[' +
        ',\n'.join(json.dumps(i) for i in data) +
        ']\n')

结果：

import json

data = [
    {"key01":"value","key02":"value"},
    {"key11":"value","key12":"value"},
    {"key21":"value","key22":"value"}
]

import json
with open('file.json', 'w') as fp:
    fp.write(
        '[' +
        ',\n'.join(json.dumps(i) for i in data) +
        ']\n')

Answer 2

为了好玩，我将我的答案改编为另一个有些相关的问题，以使其满足您的要求。请注意，目前它仅更改dict列表中的 a 的格式。

import _ctypes
import json
import re

class OneDictPerLine(object):
    def __init__(self, value):
        self.value = value
    def __repr__(self):
        if not isinstance(self.value, list):
            return repr(self.value)
        else:  # Sort the representation of any dicts in the list.
            reps = ('{{{}}}'.format(', '.join(
                        ('{!r}: {}'.format(k, v) for k, v in sorted(v.items()))
                    )) if isinstance(v, dict)
                        else
                    repr(v) for v in self.value)
            return '[' + ',\n'.join(reps) + ']'


def di(obj_id):
    """ Reverse of id() function. """
    # from /sf/answers/1050897011/
    return _ctypes.PyObj_FromPtr(obj_id)


class MyEncoder(json.JSONEncoder):
    FORMAT_SPEC = "@@{}@@"
    regex = re.compile(FORMAT_SPEC.format(r"(\d+)"))

    def default(self, obj):
        return (self.FORMAT_SPEC.format(id(obj)) if isinstance(obj, OneDictPerLine)
                else super(MyEncoder, self).default(obj))

    def encode(self, obj):
        format_spec = self.FORMAT_SPEC  # Local var to expedite access.
        json_repr = super(MyEncoder, self).encode(obj)  # Default JSON repr.

        # Replace any marked-up object ids in the JSON repr with the value
        # returned from the repr() of the corresponding Python object.
        for match in self.regex.finditer(json_repr):
            id = int(match.group(1))
            # Replace marked-up id with actual Python object repr().
            json_repr = json_repr.replace(
                       '"{}"'.format(format_spec.format(id)), repr(di(id)))

        return json_repr

使用示例：

# Sample usage
data = [
    {"key01":"value","key02":"value"},
    {"key11":"value","key12":"value"},
    {"key21":"value","key22":"value"},
    {'key{:02d}:"value"'.format(k) for k in range(100)}
]

print(json.dumps(OneDictPerLine(data), cls=MyEncoder))

输出：

import _ctypes
import json
import re

class OneDictPerLine(object):
    def __init__(self, value):
        self.value = value
    def __repr__(self):
        if not isinstance(self.value, list):
            return repr(self.value)
        else:  # Sort the representation of any dicts in the list.
            reps = ('{{{}}}'.format(', '.join(
                        ('{!r}: {}'.format(k, v) for k, v in sorted(v.items()))
                    )) if isinstance(v, dict)
                        else
                    repr(v) for v in self.value)
            return '[' + ',\n'.join(reps) + ']'


def di(obj_id):
    """ Reverse of id() function. """
    # from https://stackoverflow.com/a/15012814/355230
    return _ctypes.PyObj_FromPtr(obj_id)


class MyEncoder(json.JSONEncoder):
    FORMAT_SPEC = "@@{}@@"
    regex = re.compile(FORMAT_SPEC.format(r"(\d+)"))

    def default(self, obj):
        return (self.FORMAT_SPEC.format(id(obj)) if isinstance(obj, OneDictPerLine)
                else super(MyEncoder, self).default(obj))

    def encode(self, obj):
        format_spec = self.FORMAT_SPEC  # Local var to expedite access.
        json_repr = super(MyEncoder, self).encode(obj)  # Default JSON repr.

        # Replace any marked-up object ids in the JSON repr with the value
        # returned from the repr() of the corresponding Python object.
        for match in self.regex.finditer(json_repr):
            id = int(match.group(1))
            # Replace marked-up id with actual Python object repr().
            json_repr = json_repr.replace(
                       '"{}"'.format(format_spec.format(id)), repr(di(id)))

        return json_repr