`getattr()`

The built-in getattr() function allows you to retrieve the value of an attribute from an object. If the specified attribute doesn’t exist, it can return a default value if provided. Otherwise, it raises an AttributeError exception:

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

>>> jane = Person("Jane", 25)
>>> getattr(jane, "name")
'Jane'

>>> getattr(jane, "age")
25

>>> getattr(jane, "missing", None)
None

`getattr()` Signatures

getattr(object, name)
getattr(object, name, default)

Arguments

Argument	Description
`object`	The object whose attribute value you want to retrieve.
`name`	A string representing the name of the attribute to retrieve.
`default`	An optional value to return if the attribute isn’t found.

Return Value

If the attribute exists, getattr() returns the value of the attribute.
If the attribute doesn’t exist and a default value is provided, it returns the default value.
If the attribute doesn’t exist and no default value is provided, it raises an AttributeError exception.

To see how these three rules play out, try the widget below. Pick an attribute name, toggle whether you pass a default, and watch which branch getattr() takes:

The examples that follow walk through each of these three branches in code.

`getattr()` Examples

With the name of an existing attribute:

>>> class Circle:
...     def __init__(self, radius):
...         self.radius = radius
...

>>> circle = Circle(10)
>>> getattr(circle, "radius")
10

With a non-existent attribute and a default value:

>>> getattr(circle, "diameter", 0)
0

With a non-existent attribute without a default value:

>>> getattr(circle, "diameter")
Traceback (most recent call last):
  ...
AttributeError: 'Circle' object has no attribute 'diameter'

`getattr()` Common Use Cases

The most common use cases for the getattr() function include:

Accessing object attributes dynamically when attribute names are determined at runtime.
Providing a default value for non-existent attributes to avoid exceptions.
Accessing methods dynamically to call them later.

`getattr()` Real-World Example

Consider a situation where you have a list of objects, and you need to retrieve a specific attribute from each object, handling cases where the attribute might be missing by using a default value:

>>> class Car:
...     def __init__(self, make, model, year):
...         self.make = make
...         self.model = model
...         self.year = year
...

>>> cars = [
...     Car("Toyota", "Corolla", 2020),
...     Car("Ford", "Mustang", 2018),
...     Car("Tesla", "Model S", 2022)
... ]

>>> for car in cars:
...     print(getattr(car, "color", "Unknown"))
...
Unknown
Unknown
Unknown

In this example, getattr() helps retrieve the .color attribute from each Car object, providing a default value of "Unknown" when the attribute isn’t present.

Tutorial

Object-Oriented Programming (OOP) in Python

In this tutorial, you'll learn all about object-oriented programming (OOP) in Python. You'll learn the basics of the OOP paradigm and cover concepts like classes and inheritance. You'll also see how to instantiate an object from a class.

intermediate python

For additional information on related topics, take a look at the following resources: