python - How to access (get or set) object attribute given string corresponding to name of that attribute

Python - How to access (get or set) object attribute given string corresponding to name of that attribute

You can access object attributes dynamically in Python using the getattr() and setattr() functions. These functions allow you to get and set object attributes by name, given a string corresponding to the name of the attribute.

Get Object Attribute by Name:

class MyClass: def __init__(self): self.name = "John" self.age = 30 obj = MyClass() # Get attribute by name attribute_name = "name" value = getattr(obj, attribute_name) print(value) # Output: John

Set Object Attribute by Name:

class MyClass: def __init__(self): self.name = "John" self.age = 30 obj = MyClass() # Set attribute by name attribute_name = "name" setattr(obj, attribute_name, "Alice") print(obj.name) # Output: Alice

Handling Non-Existent Attribute:

If the attribute does not exist, getattr() will raise an AttributeError exception. You can provide a default value as the third argument to getattr() to handle this case:

class MyClass: def __init__(self): self.name = "John" self.age = 30 obj = MyClass() # Get non-existent attribute with default value attribute_name = "address" default_value = "Unknown" value = getattr(obj, attribute_name, default_value) print(value) # Output: Unknown

Note:

  • Ensure that the attribute name string corresponds to the actual attribute name of the object. Using an incorrect attribute name may result in an AttributeError.
  • If you are dynamically accessing attributes based on user input or external data, ensure proper validation to prevent potential security vulnerabilities such as injection attacks.
  • Be mindful of Python's naming conventions. Attribute names should typically be lowercase with words separated by underscores (snake_case).

Examples

  1. Python get attribute by string name

    • Description: This query focuses on how to retrieve the value of an attribute from an object using a string that matches the attribute's name.
    • Code:
      class MyClass: def __init__(self, name, value): self.name = name self.value = value obj = MyClass('test', 123) attribute_name = 'value' attribute_value = getattr(obj, attribute_name) print(attribute_value) # Output: 123

  2. Python set attribute by string name

    • Description: This query addresses setting the value of an attribute on an object using a string that matches the attribute's name.
    • Code:
      class MyClass: def __init__(self, name, value): self.name = name self.value = value obj = MyClass('test', 123) attribute_name = 'value' new_value = 456 setattr(obj, attribute_name, new_value) print(obj.value) # Output: 456

  3. Python dynamic attribute access using string names

    • Description: This query focuses on accessing and modifying attributes dynamically using string names in Python.
    • Code:
      class DynamicAttributes: def __init__(self, **kwargs): for key, value in kwargs.items(): setattr(self, key, value) obj = DynamicAttributes(a=1, b=2, c=3) attribute_name = 'b' print(getattr(obj, attribute_name)) # Output: 2 setattr(obj, attribute_name, 10) print(obj.b) # Output: 10

  4. Using getattr and setattr for attribute manipulation in Python

    • Description: This query covers using getattr and setattr to manipulate object attributes dynamically.
    • Code:
      class Person: def __init__(self, name, age): self.name = name self.age = age p = Person('Alice', 30) attr_name = 'age' print(getattr(p, attr_name)) # Output: 30 setattr(p, attr_name, 35) print(p.age) # Output: 35

  5. Accessing object attributes with string variable names in Python

    • Description: This query focuses on how to use string variable names to access object attributes in Python.
    • Code:
      class Car: def __init__(self, make, model): self.make = make self.model = model my_car = Car('Toyota', 'Corolla') attribute_name = 'make' car_make = getattr(my_car, attribute_name) print(car_make) # Output: Toyota

  6. Python dynamically get and set object properties

    • Description: This query addresses dynamically getting and setting object properties in Python.
    • Code:
      class Item: def __init__(self, name, price): self.name = name self.price = price item = Item('Laptop', 1000) prop_name = 'price' print(getattr(item, prop_name)) # Output: 1000 setattr(item, prop_name, 1200) print(item.price) # Output: 1200

  7. How to use getattr and setattr in Python for dynamic attribute management

    • Description: This query focuses on using getattr and setattr for dynamic attribute management in Python.
    • Code:
      class User: def __init__(self, username, email): self.username = username self.email = email user = User('john_doe', 'john@example.com') attr_to_get = 'email' print(getattr(user, attr_to_get)) # Output: john@example.com attr_to_set = 'email' new_value = 'john.doe@example.com' setattr(user, attr_to_set, new_value) print(user.email) # Output: john.doe@example.com

  8. Dynamic attribute access in Python with getattr and setattr

    • Description: This query focuses on how to dynamically access and modify attributes using getattr and setattr.
    • Code:
      class Book: def __init__(self, title, author): self.title = title self.author = author book = Book('1984', 'George Orwell') attribute = 'title' print(getattr(book, attribute)) # Output: 1984 setattr(book, attribute, 'Animal Farm') print(book.title) # Output: Animal Farm

  9. How to manipulate object attributes in Python using string keys

    • Description: This query covers manipulating object attributes in Python using string keys.
    • Code:
      class Product: def __init__(self, name, price): self.name = name self.price = price product = Product('Phone', 699) attr_name = 'name' print(getattr(product, attr_name)) # Output: Phone setattr(product, attr_name, 'Smartphone') print(product.name) # Output: Smartphone

  10. Access and modify attributes of an object using string names in Python

    • Description: This query focuses on accessing and modifying attributes of an object using string names.
    • Code:
      class Employee: def __init__(self, id, department): self.id = id self.department = department emp = Employee(101, 'Sales') attribute_name = 'department' print(getattr(emp, attribute_name)) # Output: Sales setattr(emp, attribute_name, 'Marketing') print(emp.department) # Output: Marketing

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