Python get all fields in class

Get a List of Class Attributes in Python

Python classes are mostly templates for creating new objects. The contents/attributes of the objects belonging to a class are described by the class.

What exactly are class attributes?

Class attributes are nothing but variables of a class. It is important to note that these variables are shared between all the instances of the class.

class example: z=5 obj1=example() print(obj1.z) obj2=example() print(obj1.z+obj2.z)

In the above example code, z is a class attribute and is shared by the class instances obj1 and obj2.

In this tutorial, you will learn how to fetch a list of the class attributes in Python.

Using the dir() method to find all the class attributes

It returns a list of the attributes and methods of the passed object/class. On being called upon class objects, it returns a list of names of all the valid attributes and base attributes too.

Syntax: dir(object) , where object is optional.

Here, you can obtain the list of class attributes;

By passing the class itself

class example: z=5 obj1=example() print(obj1.z) obj2=example() print(obj1.z+obj2.z) print(dir(example)) #By passing the class itself

5 10 ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'z']

class example: z=5 obj1=example() print(obj1.z) obj2=example() print(obj1.z+obj2.z) print(dir(obj1)) #By passing the object of class

5 10 ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'z']

However, the dir() method also returns the magic methods of the class along with the class attributes.

By using __dict__ get class attributes

It stores/returns a dictionary of the attributes that describe an object. Let us understand the same by looking into an example.

class fruit(): def __init__(self,fruitname,color): self.name=fruitname self.color=color apple=fruit("apple","red") print(apple.name) print(apple.color) print(apple.__dict__)

Here, apple is an object belonging to class fruit. So, the __dict__ has returned a dictionary that contains the attributes of the object i.e., apple.

Also, you can further get just the keys or values for the particular object by using the dictionary’s key, value system of storage.

class fruit(): def __init__(self,fruitname,color): self.name=fruitname self.color=color apple=fruit("apple","red") print(apple.name) print(apple.color) print(apple.__dict__) print(apple.__dict__.keys()) print(apple.__dict__.values())

apple red dict_keys(['name', 'color']) dict_values(['apple', 'red'])

By using the inspect module’s getmembers()

The getmembers() function retrieves the members of an object such as a class in a list.

import inspect class fruit(): def __init__(self,fruitname,color): self.name=fruitname self.color=color apple=fruit("apple","red") print(inspect.getmembers(apple))

[('__class__', ), ('__delattr__', ), ('__dict__', ), ('__dir__', ), ('__doc__', None), ('__eq__', ), ('__format__', ), ('__ge__', ), ('__getattribute__', ), ('__gt__', ), ('__hash__', ), ('__init__', >), ('__init_subclass__', ), ('__le__', ), ('__lt__', ), ('__module__', '__main__'), ('__ne__', ), ('__new__', ), ('__reduce__', ), ('__reduce_ex__', ), ('__repr__', ), ('__setattr__', ), ('__sizeof__', ), ('__str__', ), ('__subclasshook__', ), ('__weakref__', None), ('color', 'red'), ('name', 'apple')]

To get a list of just the passed object’s attribute, i.e., to remove all the public and private in-built attributes/magic methods from the list;

import inspect class fruit(): def __init__(self,fruitname,color): self.name=fruitname self.color=color apple=fruit("apple","red") for i in inspect.getmembers(apple): if not i[0].startswith('_'): if not inspect.ismethod(i[1]): print(i)

Using the vars() method

It takes an object as a parameter and returns its attributes.

import inspect class fruit(): def __init__(self,fruitname,color): self.name=fruitname self.color=color apple=fruit("apple","red") print(vars(apple))

However, you must observe that the above two methods return the class attributes only for the respective base class.

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How to list all fields of a class (and no methods)?

You can get it via the __dict__ attribute, or the built-in vars function, which is just a shortcut:

>>> class A(object): . foobar = 42 . def __init__(self): . self.foo = 'baz' . self.bar = 3 . def method(self, arg): . return True . >>> a = A() >>> a.__dict__ >>> vars(a)

There’s only attributes of the object. Methods and class attributes aren’t present.

Maxime Lorant 32686

Similar question

You can iterate through an instance’s __dict__ attribute and look for non-method things. For example:

CALLABLES = types.FunctionType, types.MethodType for key, value in A().__dict__.items(): if not isinstance(value, CALLABLES): print(key) 

You can do it in a single statement with a list comprehension:

print(Python get all fields in class) 

Which would print [‘foo’, ‘bar’] .

martineau 115235

This should work for callables:

[f for f in dir(o) if not callable(getattr(o,f))] 

You could get rid of the rest with:

[f for f in dir(o) if not callable(getattr(o,f)) and not f.startswith('__')] 

Benjamin Toueg 10002

The basic answer is «you can’t do so reliably». See this question.

You can get an approximation with [attr for attr in dir(obj) if attr[:2] + attr[-2:] != ‘____’ and not callable(getattr(obj,attr))] .

However, you shouldn’t rely on this, because:

Because dir() is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases.

In other words, there is no canonical way to get a list of «all of an object’s attributes» (or «all of an object’s methods»).

If you’re doing some kind of dynamic programming that requires you to iterate over unknwon fields of an object, the only reliable way to do it is to implement your own way of keeping track of those fields. For instance, you could use an attribute naming convention, or a special «fields» object, or, most simply, a dictionary.

BrenBarn 232614

You could use the built-in method vars()

El Bert 2908

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