__getitem__() in Python

As Python developers, we have all had those moments when we sense as our code has magically come together. One of the key components in this magical level is Python's use of "magic methods," which enable our code to act in intuitive and human-friendly approaches. In this newsletter, we will pay attention to the getitem() magic method, unraveling its secrets and techniques and uncovering the effective blessings it brings to our code. Let's get started!

The Allure of Magic Methods

Magic methods are unique techniques in Python instructions which have double underscores at the start and end of their names, earning them the nickname "dunder" methods (brief for "double underscore"). These strategies permit us to define how our instructions need to behave in particular situations, making them extra flexible and expressive. One of those magic strategies is getitem(), which is used to define how we retrieve factors from custom instructions.

The Power of Getitem()

The getitem() magic method lets us define a way to get the right of entry to factors of a custom class using the square bracket notation, similar to what we might do with lists, dictionaries, or other built-in Python objects. When we define a class with a getitem() approach, we will get the right of entry to its factors through the use of the familiar syntax −

element = my_instance[index]

Let's look at an example of a simple custom class called MyList, which simulates a basic list using the getitem() magic method −

Step 1  Define the MyList class with a constructor (__init__) that takes a listing as input and keeps it inside the data attribute. This constructor is called while we create a brand new instance of MyList and initialize the example with the data presented.

Step 2  Execute the __getitem__() method to get access to elements using the index.

Step 3  Create an instance of MyList with a list of numbers from 1 to 5. The constructor stores the provided listing within the data attribute of the instance.

Step 4  Print the element at index 1 using the square bracket notation, outputting 2.


class MyList:
   def __init__(self, data):
      self.data = data
   def __getitem__(self, index):
      return self.data[index]

my_list = MyList([1, 2, 3, 4, 5])



Making Your Code More Intuitive

By implementing the getitem() magic method in our custom classes, we can make our code more intuitive and human-friendly. Here are some tips for leveraging the power of getitem() effectively −

  • Aim for familiar behavior  When implementing getitem(), try to make the behavior resemble built-in Python objects like lists, dictionaries, or arrays. This will make your custom classes more approachable and easier to understand.

  • Handle edge cases gracefully  Be prepared to handle edge cases, such as invalid indices or keys. You can raise appropriate exceptions, like IndexError for invalid indices or KeyError for invalid keys, to inform users about the issue.

  • Support slicing  Consider supporting slicing operations in your getitem() method, making your custom classes even more versatile and convenient to work with.

  • Use clear variable names  When defining your getitem() method, use clear and descriptive variable names for indices and values. This will make your code more readable and less difficult to manage.

  • Stay consistent  If your class implements each getitem() and other related magic techniques (e.g., setitem() or delitem()), make certain their behavior stays steady. For instance, if your getitem() method supports negative indices, your other methods should do the same.


In this article, we've delved into the world of Python's getitem() magic method, exploring how it brings a readability to our code by enabling intuitive and expressive element access. By following the tips we've discussed, you'll be able to harness the power of getitem()

Updated on: 09-May-2023


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