Python到JSON序列化在十进制失败[重复]

Question

谢了。下面是我的代码。看起来dumps（）甚至没有进入专用编码器。

clayton@mserver:~/python> cat test1.py
import json, decimal

class DecimalEncoder(json.JSONEncoder):
        def _iterencode(self, o, markers=None):
                print "here we go o is a == ", type(o)
                if isinstance(o, decimal.Decimal):
                        print "woohoo! got a decimal"
                        return (str(o) for o in [o])
                return super(DecimalEncoder, self)._iterencode(o, markers)

z = json.dumps( {'x': decimal.Decimal('5.5')}, cls=DecimalEncoder )
print z
clayton@mserver:~/python> python test1.py
Traceback (most recent call last):
  File "test1.py", line 11, in <module>
    z = json.dumps( {'x': decimal.Decimal('5.5')}, cls=DecimalEncoder )
  File "/home/clayton/python/Python-2.7.3/lib/python2.7/json/__init__.py", line 238, in dumps
    **kw).encode(obj)
  File "/home/clayton/python/Python-2.7.3/lib/python2.7/json/encoder.py", line 201, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/home/clayton/python/Python-2.7.3/lib/python2.7/json/encoder.py", line 264, in iterencode
    return _iterencode(o, 0)
  File "/home/clayton/python/Python-2.7.3/lib/python2.7/json/encoder.py", line 178, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: Decimal('5.5') is not JSON serializable
clayton@mserver:~/python>

Answer 1

它不（不再）建议您创建子类；json.dump()和json.dumps()函数采用default函数：

def decimal_default(obj):
    if isinstance(obj, decimal.Decimal):
        return float(obj)
    raise TypeError

json.dumps({'x': decimal.Decimal('5.5')}, default=decimal_default)

演示：

>>> def decimal_default(obj):
...     if isinstance(obj, decimal.Decimal):
...         return float(obj)
...     raise TypeError
... 
>>> json.dumps({'x': decimal.Decimal('5.5')}, default=decimal_default)
'{"x": 5.5}'

您找到的代码只在Python 2.6上工作，并且重写了一个在以后的版本中不再调用的私有方法。