Python setattr(), getattr(), hasattr() functions

In Python, setattr(), getattr(), and hasattr() are built-in functions that allow you to interact with an object's attributes dynamically. These functions can be particularly useful when you want to manipulate attributes of an object without knowing their names beforehand.

Here's a tutorial on how to use setattr(), getattr(), and hasattr() in Python:

Define a class with some instance attributes:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

Create an instance of the class:

person = Person("Alice", 30)

Use setattr() to set the value of an attribute: setattr(object, attribute_name, value) sets the value of the attribute attribute_name of object to value. If the attribute doesn't exist, it will be created.

setattr(person, "name", "Bob")
setattr(person, "email", "bob@example.com")
print(person.name)   # Output: Bob
print(person.email)  # Output: bob@example.com

Use getattr() to get the value of an attribute: getattr(object, attribute_name, default_value) returns the value of the attribute attribute_name of object. If the attribute doesn't exist and default_value is provided, it returns default_value; otherwise, it raises an AttributeError.

name = getattr(person, "name")
age = getattr(person, "age")
city = getattr(person, "city", "New York")

print(name)  # Output: Bob
print(age)   # Output: 30
print(city)  # Output: New York

Use hasattr() to check if an object has a specific attribute: hasattr(object, attribute_name) returns True if the object has an attribute with the name attribute_name, and False otherwise.

has_name = hasattr(person, "name")
has_city = hasattr(person, "city")

print(has_name)  # Output: True
print(has_city)  # Output: False

In this tutorial, you learned how to use setattr(), getattr(), and hasattr() in Python to dynamically set, get, and check the existence of attributes for an object. These functions are especially useful when working with attributes whose names are determined at runtime or when you want to manipulate attributes in a more generic and flexible manner.

Using setattr() to set attributes dynamically in Python:

The setattr() function is used to set the value of an attribute on an object.

class DynamicAttributes:
    pass

obj = DynamicAttributes()
setattr(obj, 'attribute', 'dynamic_value')
print(obj.attribute)  # Output: dynamic_value

Dynamic attribute assignment with setattr() in Python:

class DynamicAssignment:
    pass

obj = DynamicAssignment()
attribute_name = 'dynamic_attribute'
attribute_value = 'assigned_value'
setattr(obj, attribute_name, attribute_value)
print(getattr(obj, attribute_name))  # Output: assigned_value

Python getattr() function for attribute retrieval:

The getattr() function retrieves the value of an attribute from an object.

class DynamicAttributes:
    attribute = 'example_value'

obj = DynamicAttributes()
value = getattr(obj, 'attribute')
print(value)  # Output: example_value

How to use getattr() to access attributes in Python:

class DynamicAttributes:
    attribute = 'example_value'

obj = DynamicAttributes()
attribute_name = 'attribute'
value = getattr(obj, attribute_name)
print(value)  # Output: example_value

Checking attribute existence with hasattr() in Python:

The hasattr() function checks if an object has a given attribute.

class DynamicAttributes:
    attribute = 'example_value'

obj = DynamicAttributes()
has_attribute = hasattr(obj, 'attribute')
print(has_attribute)  # Output: True

Dynamic attribute checking with hasattr() in Python:

class DynamicAttributes:
    attribute = 'example_value'

obj = DynamicAttributes()
attribute_name = 'attribute'
has_attribute = hasattr(obj, attribute_name)
print(has_attribute)  # Output: True

Setting and getting attributes with setattr() and getattr():

class DynamicAttributes:
    pass

obj = DynamicAttributes()
attribute_name = 'dynamic_attribute'
attribute_value = 'assigned_value'

setattr(obj, attribute_name, attribute_value)
retrieved_value = getattr(obj, attribute_name)

print(retrieved_value)  # Output: assigned_value

Attribute manipulation using setattr() and getattr() in Python:

class DynamicManipulation:
    pass

obj = DynamicManipulation()
attribute_name = 'dynamic_attribute'
setattr(obj, attribute_name, 'initial_value')

# Perform some operations
current_value = getattr(obj, attribute_name)
setattr(obj, attribute_name, current_value * 2)

print(getattr(obj, attribute_name))  # Output: initial_valueinitial_value

Dynamically handling missing attributes with hasattr():

class DynamicHandling:
    def __getattr__(self, name):
        return f"Attribute '{name}' not found."

obj = DynamicHandling()
print(obj.undefined_attribute)  # Output: Attribute 'undefined_attribute' not found.

Using setattr() and getattr() for object introspection in Python:

class IntrospectionExample:
    def __init__(self, attribute1, attribute2):
        self.attribute1 = attribute1
        self.attribute2 = attribute2

obj = IntrospectionExample(attribute1='value1', attribute2='value2')

for attr_name in dir(obj):
    if not attr_name.startswith('__'):
        print(f"{attr_name}: {getattr(obj, attr_name)}")

Error handling with setattr(), getattr(), and hasattr() in Python:

class ErrorHandling:
    pass

obj = ErrorHandling()

try:
    value = getattr(obj, 'undefined_attribute')
except AttributeError as e:
    print(f"Error: {e}")