python create object with attributes

How can I create an object and add attributes to it?

stackoverflow.com › questions › 2827623 › how-can-i-create-an-object-and-add-attributes-to-it

The built-in object can be instantiated but can't have any attributes set on it. (I wish it could, for this exact purpose.) This is because it doesn't have a __dict__ to hold the attributes.

I generally just do this:

class Object(object):
    pass

obj = Object()
obj.somefield = "somevalue"

But consider giving the Object class a more meaningful name, depending on what data it holds.

Another possibility is to use a sub-class of dict that allows attribute access to get at the keys:

class AttrDict(dict):
    def __getattr__(self, key):
        return self[key]

    def __setattr__(self, key, value):
        self[key] = value

obj = AttrDict()
obj.somefield = "somevalue"

To instantiate the object attributes using a dictionary:

d = {"a": 1, "b": 2, "c": 3}

for k, v in d.items():
    setattr(obj, k, v)

Answer from FogleBird on Stack Overflow

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python - How can I create an object and add attributes to it? - Stack Overflow

Top answer

1 of 16

494

The built-in object can be instantiated but can't have any attributes set on it. (I wish it could, for this exact purpose.) This is because it doesn't have a __dict__ to hold the attributes.

I generally just do this:

class Object(object):
    pass

obj = Object()
obj.somefield = "somevalue"

But consider giving the Object class a more meaningful name, depending on what data it holds.

Another possibility is to use a sub-class of dict that allows attribute access to get at the keys:

class AttrDict(dict):
    def __getattr__(self, key):
        return self[key]

    def __setattr__(self, key, value):
        self[key] = value

obj = AttrDict()
obj.somefield = "somevalue"

To instantiate the object attributes using a dictionary:

d = {"a": 1, "b": 2, "c": 3}

for k, v in d.items():
    setattr(obj, k, v)

2 of 16

301

You could use my ancient Bunch recipe, but if you don't want to make a "bunch class", a very simple one already exists in Python -- all functions can have arbitrary attributes (including lambda functions). So, the following works:

obj = lambda: None
obj.somefield = 'somevalue'

Whether the loss of clarity compared to the venerable Bunch recipe is OK, is a style decision I will of course leave up to you.

Why can't you add attributes to object in python?

Giving attributes to an object in Python

python 3.x - Adding a attribute to an instance

python - More Pythonic way of adding attributes to class?

python - Attribute assignment to built-in object

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June 7, 2023 - You can create a Python object with attributes by defining a class with the desired attributes and initializing them within the init method.

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Shortest way of creating an object with arbitrary attributes in Python? - Stack Overflow

Unfortunately, most code I write is limited to Python 2.5, and namedtuple was added in 2.6. +1 though =) 2010-02-17T12:03:44.483Z+00:00 ... I just meant that I could go with a simpler solution, this solution has extra tuple functionality that I don't really need (plus it creates a whole new class; I was just interested in creating a single instance with the specified attributes ... More on stackoverflow.com

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Working with objects with many attributes - best approach?

To first reply to your concern about the "pythonic" way to do this, in scenarios like this it really comes down to what is the most concise, explicit, and logical way to do what you're trying to do. With that in mind, I'll have some suggestions for you. Given that when you are instantiating your Platform class, you already have access to all the xml elements/information, I think the most reasonable approach is to let the Platform class itself handle setting up all of its attributes for you. The more you can delegate pieces of code to their constituent parts, the better in my mind. as far as your suggested solutions, I think a combination would be best to keep your class more flexible for future potential uses. By that I mean adding an optuonal parameter for a list of the xml element objects you have in your outer for loop and making a method inside the Platform class that pulls out the constituent parts, as well as taking advantage of the **kwargs python parameter to allow the instance variables to be passed in manually as well. A simple way to do this is using the dictionaries get method and using the secondary default value parameter like so: self.variable = kwargs.get (var_name, default_value) An implementation like that, I think, will give you a very logical solution to your that is flexible and extensible for any unforseen future needs. Edit: I would recommend not using the set attr builtin for a situation like this, or if you do, only do so under the pretense of the has attr method. Remember the python guideline explicit is better than inplicit, and remember that with the code you have now, your Platform instances could end up with a bunch of attributes you may not have intended them to have. Which could cause confusion later on. I think in this case it's better to make sure you only process the xml elements you actually support in your Platform class, rather than adding any element in the xml you find to your class. Edit 2: the above also applies to the Platforms str method, printing out the classes entire dict is a little lazy and will give you a lot of clutter you probably don't care about (python builtin variables and the likes). Edit 3: it also kind of looks like everything other than the first 3 attributes of the class may be better suited in a dictionary object, perhaps named properties? That way your string method has less to do, and the kwargs dictionary could be precisely mapped to this internal dictionary. Using the python builtins getitem and setitem, you can emulate dictionary key access that can look inside this internal dictionary as well, so you could access these values from Platform as if platform itself were a dictionary. Just throwing this one out as something to keep in mind as it may be something you like or is helpful for your use case. More on reddit.com

r/learnpython

4

2

February 17, 2015

Can an object be an attribute of another object?

Yes. Token example: class Car: def __init__(self,model,cylinders): self.model = model self.engine = Engine(cylinders) class Engine: def __init__(self, cylinders): self.cylinders = cylinders my_car = Car("Honda CR-V",6) print(my_car.model) print(my_car.engine.cylinders) More on reddit.com

r/learnpython

4

1

August 27, 2022

dynamically add properties to a class (property, __getattribute__, something else?)

Properties must be defined on the class, not the instance. You're assigning the property on self when it needs to be assigned on A.

But dynamically creating attributes like this is weird and messy. The first thing you should do is reconsider whether you really do need to dynamically create attributes. It's an overly complex solution to most problems. Describing your problem to us might be helpful here. If you still decide you need this then you should use __getattr__ (and probably not __getattribute__). Properties are not the right solution.

Top answer

1 of 11

73

type('', (), {})() will create an object that can have arbitrary attributes.

Example:

obj = type('', (), {})()
obj.hello = "hello"
obj.world = "world"
print obj.hello, obj.world   # will print "hello world"

type() with three arguments creates a new type.

The first argument '' is the name of the new type. We don't care about the name, so we leave it empty.
The second argument () is a tuple of base types. Here object is implicit.
The third argument is a dictionary of attributes of the new object. We start off with no attributes so it's empty {}.

In the end we instantiate a new instance of this new type with ().

2 of 11

34

The original code can be streamlined a little by using __dict__:

In [1]: class data:
   ...:     def __init__(self, **kwargs):
   ...:         self.__dict__.update(kwargs)
   ...: 

In [2]: d = data(foo=1, bar=2)

In [3]: d.foo
Out[3]: 1

In [4]: d.bar
Out[4]: 2

In Python 3.3 and greater, this syntax is made available by the types.SimpleNamespace class.

Iditect

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How to create an object and add attributes to it in python?

Description: This query addresses the basic process of creating a new object in Python and dynamically adding attributes to it. ... Description: Sometimes, you may need to add attributes to an object after its creation for flexibility and adaptability. ... class MyClass: pass obj = MyClass() setattr(obj, 'attribute1', "value1") setattr(obj, 'attribute2', 123) How to initialize an object with attributes in Python using the constructor?

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Class Objects in Python: How to Create an Object, How to Get Attributes

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09:07

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reddit.com › r/learnpython › working with objects with many attributes - best approach?

r/learnpython on Reddit: Working with objects with many attributes - best approach?

February 17, 2015 -

I'm working on my own version of thegamesdb api for python and I'm having an internal struggle over the best way to handle multiple sub-elements for items. For example, when you call the GetPlatform API, each platform object can have many elements. I want to create a platform object that contains all of those attributes, but I'm not sure if I should create a new Platform object within the XML parsing method and then modify the object as I read the items, read all the items first into variables and call the Platform object with a dozen or more arguments, pass a dictionary to the Platform object and parse it within init, or maybe even another idea I've yet to think of.

My current strategy is to create a new Platform object with just the id and name, then use the setattr() method on the object as I iterate over the elements, but I'm not sure if this is pythonic or not.

Any suggestions or resources on how this could should be properly written?

Github link

Top answer

1 of 1

2

To first reply to your concern about the "pythonic" way to do this, in scenarios like this it really comes down to what is the most concise, explicit, and logical way to do what you're trying to do. With that in mind, I'll have some suggestions for you. Given that when you are instantiating your Platform class, you already have access to all the xml elements/information, I think the most reasonable approach is to let the Platform class itself handle setting up all of its attributes for you. The more you can delegate pieces of code to their constituent parts, the better in my mind. as far as your suggested solutions, I think a combination would be best to keep your class more flexible for future potential uses. By that I mean adding an optuonal parameter for a list of the xml element objects you have in your outer for loop and making a method inside the Platform class that pulls out the constituent parts, as well as taking advantage of the **kwargs python parameter to allow the instance variables to be passed in manually as well. A simple way to do this is using the dictionaries get method and using the secondary default value parameter like so: self.variable = kwargs.get (var_name, default_value) An implementation like that, I think, will give you a very logical solution to your that is flexible and extensible for any unforseen future needs. Edit: I would recommend not using the set attr builtin for a situation like this, or if you do, only do so under the pretense of the has attr method. Remember the python guideline explicit is better than inplicit, and remember that with the code you have now, your Platform instances could end up with a bunch of attributes you may not have intended them to have. Which could cause confusion later on. I think in this case it's better to make sure you only process the xml elements you actually support in your Platform class, rather than adding any element in the xml you find to your class. Edit 2: the above also applies to the Platforms str method, printing out the classes entire dict is a little lazy and will give you a lot of clutter you probably don't care about (python builtin variables and the likes). Edit 3: it also kind of looks like everything other than the first 3 attributes of the class may be better suited in a dictionary object, perhaps named properties? That way your string method has less to do, and the kwargs dictionary could be precisely mapped to this internal dictionary. Using the python builtins getitem and setitem, you can emulate dictionary key access that can look inside this internal dictionary as well, so you could access these values from Platform as if platform itself were a dictionary. Just throwing this one out as something to keep in mind as it may be something you like or is helpful for your use case.

Delft Stack

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