Python dictionary from an object's fields


Do you know if there is a built-in function to build a dictionary from an arbitrary object? I’d like to do something like this:

>>> class Foo:
...     bar = 'hello'
...     baz = 'world'
>>> f = Foo()
>>> props(f)
{ 'bar' : 'hello', 'baz' : 'world' }

NOTE: It should not include methods. Only fields.

Asked By: Julio César



The dir builtin will give you all the object’s attributes, including special methods like __str__, __dict__ and a whole bunch of others which you probably don’t want. But you can do something like:

>>> class Foo(object):
...     bar = 'hello'
...     baz = 'world'
>>> f = Foo()
>>> [name for name in dir(f) if not name.startswith('__')]
[ 'bar', 'baz' ]
>>> dict((name, getattr(f, name)) for name in dir(f) if not name.startswith('__')) 
{ 'bar': 'hello', 'baz': 'world' }

So can extend this to only return data attributes and not methods, by defining your props function like this:

import inspect

def props(obj):
    pr = {}
    for name in dir(obj):
        value = getattr(obj, name)
        if not name.startswith('__') and not inspect.ismethod(value):
            pr[name] = value
    return pr
Answered By: dF.

I’ve settled with a combination of both answers:

dict((key, value) for key, value in f.__dict__.iteritems() 
    if not callable(value) and not key.startswith('__'))
Answered By: Julio César

Note that best practice in Python 2.7 is to use new-style classes (not needed with Python 3), i.e.

class Foo(object):

Also, there’s a difference between an ‘object’ and a ‘class’. To build a dictionary from an arbitrary object, it’s sufficient to use __dict__. Usually, you’ll declare your methods at class level and your attributes at instance level, so __dict__ should be fine. For example:

>>> class A(object):
...   def __init__(self):
...     self.b = 1
...     self.c = 2
...   def do_nothing(self):
...     pass
>>> a = A()
>>> a.__dict__
{'c': 2, 'b': 1}

A better approach (suggested by robert in comments) is the builtin vars function:

>>> vars(a)
{'c': 2, 'b': 1}

Alternatively, depending on what you want to do, it might be nice to inherit from dict. Then your class is already a dictionary, and if you want you can override getattr and/or setattr to call through and set the dict. For example:

class Foo(dict):
    def __init__(self):
    def __getattr__(self, attr):
        return self[attr]

    # etc...
Answered By: user6868

To build a dictionary from an arbitrary object, it’s sufficient to use __dict__.

This misses attributes that the object inherits from its class. For example,

class c(object):
    x = 3
a = c()

hasattr(a, ‘x’) is true, but ‘x’ does not appear in a.__dict__

Answered By: indentation

Late answer but provided for completeness and the benefit of googlers:

def props(x):
    return dict((key, getattr(x, key)) for key in dir(x) if key not in dir(x.__class__))

This will not show methods defined in the class, but it will still show fields including those assigned to lambdas or those which start with a double underscore.

Answered By: Score_Under

I think the easiest way is to create a getitem attribute for the class. If you need to write to the object, you can create a custom setattr . Here is an example for getitem:

class A(object):
    def __init__(self):
        self.b = 1
        self.c = 2
    def __getitem__(self, item):
        return self.__dict__[item]

# Usage: 
a = A()
a.__getitem__('b')  # Outputs 1
a.__dict__  # Outputs {'c': 2, 'b': 1}
vars(a)  # Outputs {'c': 2, 'b': 1}

dict generates the objects attributes into a dictionary and the dictionary object can be used to get the item you need.

Answered By: radtek

I thought I’d take some time to show you how you can translate an object to dict via dict(obj).

class A(object):
    d = '4'
    e = '5'
    f = '6'

    def __init__(self):
        self.a = '1'
        self.b = '2'
        self.c = '3'

    def __iter__(self):
        # first start by grabbing the Class items
        iters = dict((x,y) for x,y in A.__dict__.items() if x[:2] != '__')

        # then update the class items with the instance items

        # now 'yield' through the items
        for x,y in iters.items():
            yield x,y

a = A()
# prints "{'a': '1', 'c': '3', 'b': '2', 'e': '5', 'd': '4', 'f': '6'}"

The key section of this code is the __iter__ function.

As the comments explain, the first thing we do is grab the Class items and prevent anything that starts with ‘__’.

Once you’ve created that dict, then you can use the update dict function and pass in the instance __dict__.

These will give you a complete class+instance dictionary of members. Now all that’s left is to iterate over them and yield the returns.

Also, if you plan on using this a lot, you can create an @iterable class decorator.

def iterable(cls):
    def iterfn(self):
        iters = dict((x,y) for x,y in cls.__dict__.items() if x[:2] != '__')

        for x,y in iters.items():
            yield x,y

    cls.__iter__ = iterfn
    return cls

class B(object):
    d = 'd'
    e = 'e'
    f = 'f'

    def __init__(self):
        self.a = 'a'
        self.b = 'b'
        self.c = 'c'

b = B()
Answered By: Seaux

Instead of x.__dict__, it’s actually more pythonic to use vars(x).

Answered By: Berislav Lopac

If you want to list part of your attributes, override __dict__:

def __dict__(self):
    d = {
    'attr_1' : self.attr_1,
    return d

# Call __dict__
d = instance.__dict__()

This helps a lot if your instance get some large block data and you want to push d to Redis like message queue.

Answered By: coanor


class DateTimeDecoder(json.JSONDecoder):

   def __init__(self, *args, **kargs):
        JSONDecoder.__init__(self, object_hook=self.dict_to_object,
                         *args, **kargs)

   def dict_to_object(self, d):
       if '__type__' not in d:
          return d

       type = d.pop('__type__')
          dateobj = datetime(**d)
          return dateobj
          d['__type__'] = type
          return d

def json_default_format(value):
        if isinstance(value, datetime):
            return {
                '__type__': 'datetime',
                'year': value.year,
                'month': value.month,
                'hour': value.hour,
                'minute': value.minute,
                'second': value.second,
                'microsecond': value.microsecond,
        if isinstance(value, decimal.Decimal):
            return float(value)
        if isinstance(value, Enum):
            return vars(value)
    except Exception as e:
        raise ValueError

Now you can use above code inside your own class :

class Foo():
  def toJSON(self):
        return json.loads(
            json.dumps(self, sort_keys=True, indent=4, separators=(',', ': '), default=json_default_format), cls=DateTimeDecoder)

Answered By: spattanaik75

A downside of using __dict__ is that it is shallow; it won’t convert any subclasses to dictionaries.

If you’re using Python3.5 or higher, you can use jsons:

>>> import jsons
>>> jsons.dump(f)
{'bar': 'hello', 'baz': 'world'}
Answered By: R H

vars() is great, but doesn’t work for nested objects of objects

Convert nested object of objects to dict:

def to_dict(self):
    return json.loads(json.dumps(self, default=lambda o: o.__dict__))
Answered By: Ricky Levi

As mentioned in one of the comments above, vars currently isn’t universal in that it doesn’t work for objects with __slots__ instead of a normal __dict__. Moreover, some objecs (e.g., builtins like str or int) have neither a __dict__ nor __slots__.

For now, a more versatile solution could be this:

def instance_attributes(obj: Any) -> Dict[str, Any]:
    """Get a name-to-value dictionary of instance attributes of an arbitrary object."""
        return vars(obj)
    except TypeError:

    # object doesn't have __dict__, try with __slots__
        slots = obj.__slots__
    except AttributeError:
        # doesn't have __dict__ nor __slots__, probably a builtin like str or int
        return {}
    # collect all slots attributes (some might not be present)
    attrs = {}
    for name in slots:
            attrs[name] = getattr(obj, name)
        except AttributeError:
    return attrs


class Foo:
    class_var = "spam"

class Bar:
    class_var = "eggs"
    __slots__ = ["a", "b"]
>>> foo = Foo()
>>> foo.a = 1
>>> foo.b = 2
>>> instance_attributes(foo)
{'a': 1, 'b': 2}

>>> bar = Bar()
>>> bar.a = 3
>>> instance_attributes(bar)
{'a': 3}

>>> instance_attributes("baz") 


It’s a pity that this isn’t built into vars already. Many builtins in Python promise to be "the" solution to a problem but then there’s always several special cases that aren’t handled… And one just ends up having to write the code manually in any case.

Answered By: Anakhand

In 2021, and for nested objects/dicts/json use pydantic BaseModel – will convert nested dicts and nested json objects to python objects and JSON and vice versa:

>>> class Foo(BaseModel):
...     count: int
...     size: float = None
>>> class Bar(BaseModel):
...     apple = 'x'
...     banana = 'y'
>>> class Spam(BaseModel):
...     foo: Foo
...     bars: List[Bar]
>>> m = Spam(foo={'count': 4}, bars=[{'apple': 'x1'}, {'apple': 'x2'}])

Object to dict

>>> print(m.dict())
{'foo': {'count': 4, 'size': None}, 'bars': [{'apple': 'x1', 'banana': 'y'}, {'apple': 'x2', 'banana': 'y'}]}

Object to JSON

>>> print(m.json())
{"foo": {"count": 4, "size": null}, "bars": [{"apple": "x1", "banana": "y"}, {"apple": "x2", "banana": "y"}]}

Dict to object

>>> spam = Spam.parse_obj({'foo': {'count': 4, 'size': None}, 'bars': [{'apple': 'x1', 'banana': 'y'}, {'apple': 'x2', 'banana': 'y2'}]})
>>> spam
Spam(foo=Foo(count=4, size=None), bars=[Bar(apple='x1', banana='y'), Bar(apple='x2', banana='y2')])

JSON to object

>>> spam = Spam.parse_raw('{"foo": {"count": 4, "size": null}, "bars": [{"apple": "x1", "banana": "y"}, {"apple": "x2", "banana": "y"}]}')
>>> spam
Spam(foo=Foo(count=4, size=None), bars=[Bar(apple='x1', banana='y'), Bar(apple='x2', banana='y')])
Answered By: Reed Sandberg


from pprint import pformat
a_dict = eval(pformat(an_obj))
Answered By: thetaprime


return dict((key, value) for key, value in f.__dict__.items() if not callable(value) and not key.startswith('__'))
Answered By: hizbul25

Dataclass(from Python 3.7) is another option which can be used for converting class properties to dict. asdict can be used along with dataclass objects
for the conversion.


class Point:
   x: int
   y: int

p = Point(10, 20)
asdict(p) # it returns {'x': 10, 'y': 20}
Answered By: Surya Teja

Python 3.7+ in 2023

You can add the dataclass decorator to your class and define a custom JSON serializer, then json.dumps will work (and you can extend it to work with non-serializable attributes by providing a custom encoder to cls).

json.dumps(f, cls=CustomJSONEncoder)

{"bar": "hello", "baz": "world", "modified": "2023-02-08T11:49:15.675837"}

A custom JSON serializer can be easily modified to make it compatible with any type that isn’t natively JSON serializable.

from datetime import datetime
import dataclasses
import json

@dataclasses.dataclass # <<-- add this decorator 
class Foo():
    """An example dataclass."""

    bar: str = "hello"
    baz: str = "world"
    modified: datetime = Column(DateTime(timezone=True), default=datetime.utcnow)

class CustomJSONEncoder(json.JSONEncoder): # <<-- Add this custom encoder 
    """Custom JSON encoder for the DB class."""

    def default(self, o):
        if dataclasses.is_dataclass(o): # this serializes anything dataclass can handle  
            return dataclasses.asdict(o)
        if isinstance(o, datetime): # this adds support for datetime
            return o.isoformat()
        return super().default(o)

To further extend it for any non-serializable type, add another if statement to the custom encoder class that returns something serializable (e.g. str).

Answered By: Salvatore

I think the best way is to use attribute __dict__ example:

class Foo:
    def __init__(self):
        # keys are initialized with
        # their respective values = 'hello'
        self.baz = 'world'
f = Foo()
print (f.__dict__) # {'bar': 'hello', 'baz': 'world'}

sqlAlchemy example:

async def getAssessments(client_id: UUID, db: Session = Depends(get_async_session)):
    evaluation_id_data = await getEvaluationId(client_id, db)
    evaluation_id = evaluation_id_data['data']
    evaluation_dimensions_data = await getEvluationDimensions(evaluation_id, db)
    evaluation_dimensions = evaluation_dimensions_data['data']

    assessment = []
    for dimension in evaluation_dimensions:
        print(f"nn dimension {dimension} nn")
        print(f"nn dimension dict {dimension.__dict__} nn")

Where dimension is DimensionsEvaluation model object

class DimensionsEvaluation(Base):
    __tablename__ = "dimensions_evaluation"
    id = Column(Integer, primary_key=True)
    dimension_id = Column(Integer, ForeignKey(''))
    evaluation_id = Column(Integer, ForeignKey(''))
    questions = Column(String, nullable=False)
    selected = Column(Boolean, default=False)

the result is like so

 dimension <app.models.evaluation.DimensionsEvaluation object at 0x10d8def50> 

 dimension dict {'_sa_instance_state': <sqlalchemy.orm.state.InstanceState object at 0x10d8def90>, 'selected': True, 'dimension_id': 2, 'evaluation_id': 6, 'id': 16, 'questions': '[152,153]'} 

Check this link for simple example:

Answered By: DINA TAKLIT

Here is a solution that does not require any libraries and supports nested objects:

def is_json(obj: object):
    return obj is None or type(obj) in {bool, int, str, list, dict}

def attrs(obj: object):
    return {
        name: getattr(obj, name)
        for name in dir(obj)

def props(obj: object, max_depth: int=1, depth: int=0):
    if depth > max_depth:
        return {}

    return {
        name: attr if is_json(attr) else props(attr, max_depth, depth+1)
        for name, attr in attrs(obj).items()
        if not name.startswith('__') and not callable(attr)
Answered By: Marduk