如何使一个Python类序列化?
class FileItem:
def __init__(self, fname):
self.fname = fname
尝试序列化为JSON:
>>> import json
>>> x = FileItem('/foo/bar')
>>> json.dumps(x)
TypeError: Object of type 'FileItem' is not JSON serializable
如何使一个Python类序列化?
class FileItem:
def __init__(self, fname):
self.fname = fname
尝试序列化为JSON:
>>> import json
>>> x = FileItem('/foo/bar')
>>> json.dumps(x)
TypeError: Object of type 'FileItem' is not JSON serializable
当前回答
我最喜欢Lost Koder的方法。当我试图序列化成员/方法不可序列化的更复杂的对象时,我遇到了问题。这是我的实现,工作在更多的对象:
class Serializer(object):
@staticmethod
def serialize(obj):
def check(o):
for k, v in o.__dict__.items():
try:
_ = json.dumps(v)
o.__dict__[k] = v
except TypeError:
o.__dict__[k] = str(v)
return o
return json.dumps(check(obj).__dict__, indent=2)
其他回答
基于Quinten Cabo的回答:
def sterilize(obj):
"""Make an object more ameniable to dumping as json
"""
if type(obj) in (str, float, int, bool, type(None)):
return obj
elif isinstance(obj, dict):
return {k: sterilize(v) for k, v in obj.items()}
list_ret = []
dict_ret = {}
for a in dir(obj):
if a == '__iter__' and callable(obj.__iter__):
list_ret.extend([sterilize(v) for v in obj])
elif a == '__dict__':
dict_ret.update({k: sterilize(v) for k, v in obj.__dict__.items() if k not in ['__module__', '__dict__', '__weakref__', '__doc__']})
elif a not in ['__doc__', '__module__']:
aval = getattr(obj, a)
if type(aval) in (str, float, int, bool, type(None)):
dict_ret[a] = aval
elif a != '__class__' and a != '__objclass__' and isinstance(aval, type):
dict_ret[a] = sterilize(aval)
if len(list_ret) == 0:
if len(dict_ret) == 0:
return repr(obj)
return dict_ret
else:
if len(dict_ret) == 0:
return list_ret
return (list_ret, dict_ret)
区别在于
Works for any iterable instead of just list and tuple (it works for NumPy arrays, etc.) Works for dynamic types (ones that contain a __dict__). Includes native types float and None so they don't get converted to string. Classes that have __dict__ and members will mostly work (if the __dict__ and member names collide, you will only get one - likely the member) Classes that are lists and have members will look like a tuple of the list and a dictionary Python3 (that isinstance() call may be the only thing that needs changing)
这是我的3美分… 这演示了一个树状python对象的显式json序列化。 注意:如果你真的想要这样的代码,你可以使用twisted FilePath类。
import json, sys, os
class File:
def __init__(self, path):
self.path = path
def isdir(self):
return os.path.isdir(self.path)
def isfile(self):
return os.path.isfile(self.path)
def children(self):
return [File(os.path.join(self.path, f))
for f in os.listdir(self.path)]
def getsize(self):
return os.path.getsize(self.path)
def getModificationTime(self):
return os.path.getmtime(self.path)
def _default(o):
d = {}
d['path'] = o.path
d['isFile'] = o.isfile()
d['isDir'] = o.isdir()
d['mtime'] = int(o.getModificationTime())
d['size'] = o.getsize() if o.isfile() else 0
if o.isdir(): d['children'] = o.children()
return d
folder = os.path.abspath('.')
json.dump(File(folder), sys.stdout, default=_default)
我有了自己的解决办法。使用此方法,将任何文档(字典、列表、ObjectId等)传递给序列化。
def getSerializable(doc):
# check if it's a list
if isinstance(doc, list):
for i, val in enumerate(doc):
doc[i] = getSerializable(doc[i])
return doc
# check if it's a dict
if isinstance(doc, dict):
for key in doc.keys():
doc[key] = getSerializable(doc[key])
return doc
# Process ObjectId
if isinstance(doc, ObjectId):
doc = str(doc)
return doc
# Use any other custom serializting stuff here...
# For the rest of stuff
return doc
要添加另一个选项:您可以使用attrs包和asdict方法。
class ObjectEncoder(JSONEncoder):
def default(self, o):
return attr.asdict(o)
json.dumps(objects, cls=ObjectEncoder)
然后再转换回去
def from_json(o):
if '_obj_name' in o:
type_ = o['_obj_name']
del o['_obj_name']
return globals()[type_](**o)
else:
return o
data = JSONDecoder(object_hook=from_json).decode(data)
类看起来像这样
@attr.s
class Foo(object):
x = attr.ib()
_obj_name = attr.ib(init=False, default='Foo')
大多数答案都涉及更改对json.dumps()的调用,这并不总是可能的或可取的(例如,它可能发生在框架组件内部)。
如果你希望能够按原样调用json.dumps(obj),那么一个简单的解决方案是从dict继承:
class FileItem(dict):
def __init__(self, fname):
dict.__init__(self, fname=fname)
f = FileItem('tasks.txt')
json.dumps(f) #No need to change anything here
如果你的类只是基本的数据表示,这是可行的,对于更棘手的事情,你总是可以显式地设置键。