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How to Get a List of Class Attributes in Python?
  • Difficulty Level : Expert
  • Last Updated : 30 Jan, 2020

A class is a user-defined blueprint or prototype from which objects are created. Classes provide a means of bundling data and functionality together. Creating a new class creates a new type of object, allowing new instances of that type to be made. Each class instance can have attributes attached to it for maintaining its state. Class instances can also have methods (defined by its class) for modifying its state.

Example:




# Python program to demonstrate
# classes
  
  
class Student:
      
    # class variable
    stream = "COE"
      
    # Constructor
    def __init__(self, name, roll_no):
          
        self.name = name
        self.roll_no = roll_no
          
# Driver's code
a = Student("Shivam", 3425)
b = Student("Sachin", 3624)
  
print(a.stream)
print(b.stream)
print(a.name)
print(b.name)
  
# Class variables can be accessed
# using class name also 
print(Student.stream) 

Output :

COE
COE
Shivam
Sachin
COE

Note: For more information, refer to Python Classes and Objects.

Getting a List of Class Attributes

It is important to know the attributes we are working with. For small data, it is easy to remember the names of the attributes but when working with huge data, it is difficult to memorize all the attributes. Luckily, we have some functions in Python available for this task.



Method 1: To get the list of all the attributes, methods along with some inherited magic methods of a class, we use a built-in called dir().

Example:




class Number :
      
    # Class Attributes
    one = 'first'
    two = 'second'
    three = 'third'
      
    def __init__(self, attr):
        self.attr = attr
          
    def show(self): 
        print(self.one, self.two, self.three, self.attr)
          
n = Number(2)
n.show()
  
  
  
# Passing both the object 
# and class as  argument
# to the dir method
print('\nBy passing object of class')
print(dir(n))
  
print('\nBy passing class itself ')
print(dir(Number))

Output :

first second third 2

By passing object of class
[‘__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__’, ‘attr’, ‘one’, ‘show’, ‘three’, ‘two’]

By passing class itself
[‘__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__’, ‘one’, ‘show’, ‘three’, ‘two’]

Method 2: Another way of finding a list of attributes is by using the module inspect. This module provides a method called getmemebers() that returns a list of class attributes and methods.

Example 1:




import inspect
  
  
class Number :
      
    # Class Attributes
    one = 'first'
    two = 'second'
    three = 'third'
      
    def __init__(self, attr):
        self.attr = attr
          
    def show(self): 
        print(self.one, self.two, self.three, self.attr)
          
          
# Driver's code
n = Number(2)
n.show()
  
# getmembers() returns all the 
# members of an object 
for i in inspect.getmembers(n):
      
    # to remove private and protected
    # functions
    if not i[0].startswith('_'):
          
        # To remove other methods that
        # doesnot start with a underscore
        if not inspect.ismethod(i[1]): 
            print(i)

Output :

first second third 2
('attr', 2)
('one', 'first')
('three', 'third')
('two', 'second')

Method 3: To find attributes we can also use magic method __dict__. This method only returns instance attributes.

Example:




class Number :
      
    # Class Attributes
    one = 'first'
    two = 'second'
    three = 'third'
      
    def __init__(self, attr):
        self.attr = attr
          
    def show(self): 
        print(self.one, self.two, self.three, self.attr)
          
# Driver's code
n = Number(2)
n.show()
  
# using __dict__ to access attributes
# of the object n along with their values
print(n.__dict__)
  
# to only access attributes
print(n.__dict__.keys())
  
# to only access values
print(n.__dict__.values())

Output:

first second third 2
{'attr': 2}
dict_keys(['attr'])
dict_values([2])

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