相关疑难解决方法(0)

我试图子类化json.JSONEncoder这样的命名元组(使用新的Python 3.6+语法定义,但它可能仍适用于输出collections.namedtuple)被序列化为JSON对象,其中元组字段对应于对象键.

例如:

from typing import NamedTuple

class MyModel(NamedTuple):
    foo:int
    bar:str = "Hello, World!"

a = MyModel(123)           # Expected JSON: {"foo": 123, "bar": "Hello, World!"}
b = MyModel(456, "xyzzy")  # Expected JSON: {"foo": 456, "bar": "xyzzy"}

我的理解是我子类化json.JSONEncoder并覆盖它的default方法来为新类型提供序列化.然后,课程的其余部分将就递归等方面做正确的事情.因此我想出了以下内容:

class MyJSONEncoder(json.JSONEncoder):
    def default(self, o):
        to_encode = None

        if isinstance(o, tuple) and hasattr(o, "_asdict"):
            # Dictionary representation of a named tuple
            to_encode = o._asdict()

        if isinstance(o, datetime):
            # String representation of a datetime
            to_encode = …

我遇到类似于CalvinKrishy问题的问题 Samplebias的解决方案不能处理我的数据.

我使用的是Python 2.7.

这是数据:

Namedtuple

>>> a_t = namedtuple('a','f1 words')
>>> word_t = namedtuple('word','f2 value')
>>> w1 = word_t(f2=[0,1,2], value='abc')
>>> w2 = word_t(f2=[3,4], value='def')
>>> a1 = a_t(f1=[0,1,2,3,4],words=[w1, w2])
>>> a1
a(f1=[0, 1, 2, 3, 4], words=[word(f2=[0, 1, 2], value='abc'), word(f2=[3, 4], value='def')])

快译通

>>> w3 = {}
>>> w3['f2'] = [0,1,2]
>>> w3['value'] = 'abc'
>>> w4 = {}
>>> w4['f2'] = [3,4]
>>> w4['value'] = 'def'
>>> a2 = {}
>>> a2['f1'] = [0, 1, …

我无法转储collections.namedtuple为正确的 JSON。

首先，考虑使用自定义 JSON 序列化程序的官方示例：

import json

class ComplexEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, complex):
            return [obj.real, obj.imag]
        # Let the base class default method raise the TypeError
        return json.JSONEncoder.default(self, obj)

json.dumps(2 + 1j, cls=ComplexEncoder)   # works great, without a doubt

其次，现在考虑以下示例，它告诉 Python 如何对Friend对象进行 JSONize：

import json

class Friend():
    """ struct-like, for storing state details of a friend """
    def __init__(self, _id, f_name, l_name):
        self._id = _id
        self.f_name = f_name
        self.l_name = …

我正在尝试使用namedtuple将Python对象序列化为JSON.但是我得到了这个错误.谷歌没有帮助.

Traceback (most recent call last):
 File "cpu2.py", line 28, in <module>
 cpuInfo = collections.namedtuple('cpuStats',('cpu.usr', ('str(currentTime) + " " 
 +str(cpuStats[0]) + " host="+ thisClient')), ('cpu.nice', ('str(currentTime) + " " 
 +str(cpuStats[1]) + " host="+ thisClient')), ('cpu.sys',('str(currentTime) + " " 
 +str(cpuStats[2]) + " host="+ thisClient')), ('cpu.idle',('str(currentTime) + " " 
 +str(cpuStats[3]) + " host="+ thisClient')))
 TypeError: namedtuple() takes at most 4 arguments (5 given)