Adventures in Machine Learning

Streamline Your Python Code with the Walrus Operator

Introduction to the Walrus Operator

Have you ever found yourself in a situation where you needed to assign a value to a variable before using it in an expression? You might be surprised to know that there is now a more efficient way of doing this in Python, and it is called the Walrus Operator.

This operator, also known as the Colon Equals Operator, allows you to combine an assignment statement with an expression statement into a single line of code. In this article, we will explore the fundamentals of the Walrus Operator, how it is implemented in Python, and the motivation behind its creation.

Implementation of Walrus Operator

The Walrus Operator was introduced to Python through a Python Enhancement Proposal (PEP) 572 by Chris Angelico in 2018. The proposal addressed the issue of bugs, which arose from the use of assignment statements in expressions.

Guido van Rossum, the creator of Python, later approved the proposal after some modifications and contributions by Emily Morehouse. The Walrus Operator was then implemented in the alpha release of Python 3.8.

Motivation for Walrus Operator

Before the Walrus Operator, assigning a value to a variable before using it in an expression was the only option in Python. This caused code to become cluttered and harder to read in some cases.

Furthermore, some expressions required the use of multiple lines of code, further complicating their readability. With the Walrus Operator, code is now more concise and streamlined.

Walrus Operator Fundamentals

Different Terms for Walrus Operator

The “Colon Equals Operator” is not the only name this operator is known by. Another commonly used term is “Named Expressions.” Named expressions refer to the use of the Walrus Operator in creating variables with explicit names.

This helps improve code clarity and readability.

Explanation of Walrus Operator

In Python, every line of code is either a statement or an expression. A statement is a unit of code that performs an action, such as assignment or looping.

An expression is a unit of code that evaluates to a value. Before the introduction of the Walrus Operator, assigning a value to a variable and then using it in an expression was the only way to combine the two.

However, with the Walrus Operator, you can now use a single line of code to assign a value to a variable and use it in an expression.

Advantages of Using Walrus Operator

One of the key advantages of the Walrus Operator is that it improves clarity. With the operator, you do not need to create a variable and then use it in an expression.

Instead, you can combine the two into a single line of code, making it easier to read and understand. Additionally, the Walrus Operator is a convenient way to write code, since it reduces the amount of code you need to write.

This is especially useful when working with complex expressions, where you might need to assign values to several variables before using them in an expression.


In conclusion, the Walrus Operator is a useful addition to Python. It allows for more streamlined code and improves readability.

With the combination of an assignment statement and an expression into a single line of code, using the Walrus Operator can save time and make your code easier to understand. So next time you find yourself in a situation where you need to assign a variable before using it in an expression, consider using the Walrus Operator.

Implementation of Walrus Operator

In this section, we will dive deeper into the implementation of the Walrus Operator. We will cover PEP 572, which inspired its creation, the design principles behind the syntax, as well as the appropriate style for using assignment expressions.

Description of PEP 572

PEP 572 is a Python Enhancement Proposal that introduced the Walrus Operator to Python. The proposal aimed to solve the problem of readability in some expressions that required the assignment of a value to a variable before its use in an expression.

The motivation behind this proposal was to make code more concise and improve readability by making the syntax less convoluted. One example of a complex expression that motivated the creation of the Walrus Operator was the haversine formula.

This formula is used to calculate the distance between two points on a sphere. Before the introduction of the Walrus Operator, codes employing the haversine formula required several lines of code to implement, making it error-prone and less readable.

Design Principles behind Walrus Operator

One significant design principle behind the Walrus Operator was to make the new syntax backward compatible. Compatibility with previous versions of Python was important to ensure that existing code bases would not be disrupted when upgrading to the latest version of Python.

Another design principle was to make it immediately clear when a Walrus Operator was used in code. This is essential to ensure that code is still readable and understandable.

As such, the Walrus Operator must be used where it provides a significant improvement in code clarity and should not be used to jam too many complex subexpressions into a single line.

Appropriate Style for Assignment Expressions

It is important to be mindful of the appropriate style for using assignment expressions. While the syntax of the Walrus Operator is straightforward, it is essential to use traditional assignment statements when the code is more complex or difficult to read.

It is also crucial to use parentheses when the assignment expression is part of a larger expression or when the expression is long. This helps in the readability and organization of the code.

Additionally, using parentheses reduces the chances of making syntax errors when using the Walrus Operator in complex expressions.

Use Cases of Walrus Operator

In this section, we will explore some use cases of the Walrus Operator that showcase its capabilities and usefulness.

Debugging with Walrus Operator

Using the Walrus Operator can be a great way to debug complex expressions that would otherwise make the code harder to read. One example of such an expression is the haversine formula discussed earlier.

With the Walrus Operator, you can assign intermediate values to variables, making it easier to debug and understand how the calculation is done.

Lists and Dictionaries

The Walrus Operator can also be useful when working with data structures. For example, you can use it to compute descriptive statistics on a list of values.

You can also use it to split strings and assign the values to variables. The Walrus Operator can also be used to create a tuple or dictionary comprehension, which are useful when working with large data sets.

List Comprehensions

List comprehensions are a great way to optimize code, especially when dealing with computationally expensive functions. The Walrus Operator fits well with list comprehensions by optimizing loop efficiency.

Instead of using a conventional for loop, the Walrus Operator can be used to assign values to a variable within a list comprehension, increasing performance and reducing the number of lines of code.


The Walrus Operator is a new and helpful addition to Python, providing an easier way to manage assignments and expressions. Its design principles inspire clarity and readability through its syntax, making Python code easier to read and understand.

The Walrus Operator is useful in debugging complex expressions, dealing with data structures, and optimizing code with list comprehensions. Its ease of use and backward compatibility ensure the Walrus Operator is a valuable tool for Python developers.

Walrus Operator Syntax

In this section, we will take a closer look at the syntax of the Walrus Operator. We will also explore cases where the operator is not suitable, compare it with traditional assignment methods, and list some common pitfalls.

Examples of where Walrus Operator Cannot Be Used

While the Walrus Operator is useful in many cases, there are cases where it cannot be used. For instance, it is not allowed in loop targets, conditionals, and lambda expressions.

This is because these structures already provide an explicit assignment, and using the Walrus Operator in them would create ambiguity in the code, leading to syntax errors.

Comparison with Traditional Assignment Methods

The Walrus Operator provides an efficient and concise way to manage assignments within an expression, but its usage should be balanced with traditional assignment methods. The readability and efficiency of Python code are essential factors when considering the use of the operator, and balancing its usage with traditional methods can help to maintain code clarity, preventing readability issues in the future.

Readability of code is improved with traditional methods, as these methods make it clear to the reader precisely what is happening in the code. The Walrus Operator allows the integration of assignments and expressions, minimizing the appearance of necessary but redundant intermediate variables.

The operator is ideal in cases where these variables would add too much explanatory clutter to the code, for example, during a major project iteration. Efficiency is another important factor to consider when comparing traditional methods with the Walrus Operator.

The operator may lead to better performance by forcing the developer to evaluate code segments once and in the right order, saving CPU time. One must also balance this against the higher probability of syntax errors occurring, as this could slow down the development process while trying to correct them.

Walrus Operator Pitfalls

While the Walrus Operator is an excellent tool, using it too liberally can lead to some unintended consequences, including readability, clarity, and maintainability issues. One of these issues is overused Walrus Operators, leading to confusion for other developers reading the code, as it can be challenging to keep track of all the variables introduced.

Best Practices for Using Walrus Operator

Ensuring that code remains readable and clear is the most critical aspect of using the Walrus Operator. Overusing the Walrus Operator can lead to significant readability issues, making the code nearly impossible to understand for other developers.

To avoid potential issues, it is recommended that developers do not use more than one Walrus Operator per expression or force its use when a traditional method will suffice. Maintaining coding standards also plays a crucial role in ensuring the proper usage of the Walrus Operator.

All code standards should include guidelines on how and where the operator can be used, with best practices for readability, clarity, and maintainability of the code firmly in focus. Developers should also go through code reviews, testing, and QA diligently, carefully monitoring the usage and potential misuses of Walrus Operators.

By adhering to the best practices and creating regular code discussions with other developers, developers can maintain code quality while making effective use of the Walrus Operator when necessary.


In conclusion, the syntax of the Walrus Operator is simple to comprehend and can lead to more efficient and streamlined code. However, it is essential to consider readability, clarity, and maintainability when using the operator.

It is also crucial to balance the usage of the Walrus Operator with traditional methods, depending on the specific use case. Overall, by adopting the best practices discussed above, the Walrus Operator can be an invaluable tool for developers, improving coding standards and increasing efficiency in Python programming.


In this article, we have explored the fundamentals of the Walrus Operator in Python, including its implementation through Python Enhancement Proposal (PEP) 572, its syntax and design principles, and best practices for usage. We have also provided examples of where it can and cannot be used and how it compares with traditional assignment methods, as well as common pitfalls and best practices to avoid them.

Summary of Walrus Operator Features

The Walrus Operator, also known as the “Colon Equals Operator,” streamlines the creation of intermediate variables by combining assignment and expression in a single line of code. Its usage improves convenience, clarity, and readability of Python code, particularly when working with complex expressions.

It accomplishes this by allowing these expressions to be more readable and concise, by reducing the need to create additional variables and improve overall programming efficiency.

Future Developments in Python

As Python continues to evolve and grow in popularity, there will undoubtedly be further developments in the language. Guido van Rossum, Python’s creator, recently stepped down as Python’s Benevolent Dictator for Life.

As a result, Python’s open-source community created a steering council to lead the development of the language. This change has seen updates to Python’s language syntax and new feature development.

Python 3.10 will include numerous changes to the language, including new syntax features, changes to existing features, and performance improvements. One of the significant changes in the new version of Python is the structural pattern matching feature.

This new feature aims to allow the pattern matching of structural data, including lists, tuples, and dictionaries, similar to switch statement functionality found in other languages. The steering council is looking to make Python more intuitive and reduce the cognitive load for programming in Python.

For example, the council is actively encouraging the creation of more descriptive and concise function names, error messages, and library documentation.

In conclusion, the Walrus Operator is a great addition to Python that helps streamline coding while making it more readable.

It simplifies the process of creating intermediate variables by reducing the amount of code needed to accomplish this while increasing code clarity and readability. Looking ahead, it is exciting to see how these new language developments will enhance Python and how the open-source community can continue to make Python a widely adopted and user-friendly language.

In conclusion, the Walrus Operator is a powerful tool added to Python that combines the assignment and expression statements into one, making code more streamlined and readable. Its implementation, syntax, and design principles are important to understand to use it correctly and avoid any pitfalls.

Balancing the usage of the Walrus Operator with traditional assignment methods is crucial to maintaining code clarity and readability. As Python continues to evolve, new language features and updates are expected to make it more user-friendly and intuitive for developers.

Overall, by following recommended best practices, developers can utilize the Walrus Operator to write more efficient and streamlined Python code.

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