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Mastering the Python Walrus Operator Effortlessly


The Walrus Operator: Python 3.8 Assignment Expressions


The Walrus operator (:=) is a new feature introduced in Python 3.8 that allows you to assign variables within an expression. In this tutorial, we will explore the fundamentals of the Walrus operator, its use cases, syntax, pitfalls, and conclude with its importance in Python programming.

Walrus Operator Fundamentals

Hello, Walrus!

To understand the Walrus operator, let’s start with a simple example:

walrus = False
print(walrus) # False
(walrus := True)
print(walrus) # True

In the above code, on line 1, we assign the value False to the variable walrus. Then, on line 4, we use the Walrus operator to assign the value True to walrus and print it on line 6. As you can see, after both assignments, we can refer to the values using the variable name walrus.

Walrus Operator Use Cases


One of the use cases of the Walrus operator is in debugging, especially in situations where you want to print a variable value only if it meets a certain condition. For example:

import random
while (random_number := random.randint(1, 10)) != 7:
print(f"Generated: {random_number}")

In the above code, the Walrus operator is used to assign a randomly generated number to the variable random_number and check if it is not equal to 7. The loop continues until a number equal to 7 is generated. This provides a concise way of checking and printing the generated numbers without using additional lines of code.

Lists and Dictionaries

The Walrus operator can also be useful when working with lists and dictionaries. Consider the following example:

names = ["Alice", "Bob", "Charlie"]
while (name := names.pop()):

In this code, the pop() method is used to retrieve and remove the last name from the names list. The Walrus operator assigns this value to the variable name and prints it. The loop continues until there are no more names in the list, effectively printing all the names in reverse order.

List Comprehensions

List comprehensions allow you to create new lists based on existing ones. The Walrus operator can be handy in list comprehensions to simplify the code. For example:

numbers = [1, 2, 3, 4, 5]
squared_numbers = [num ** 2 for num in numbers if (num := num ** 2) < 10]
print(squared_numbers) # [1, 4]

In this code, the Walrus operator is used to assign num ** 2 to the variable num within the list comprehension. This allows us to filter the numbers that are less than 10 and create a new list with their squared values.

While Loops

The Walrus operator can make while loops more readable by combining the loop condition and the assignment. For example:

count = 0
while (count := count + 1) <= 5:

In this code, the Walrus operator is used to increment the value of count within the loop condition itself. This eliminates the need for a separate line to update the value of count and makes the code more concise.

Witnesses and Counterexamples

Another use case of the Walrus operator is in finding witnesses and counterexamples in mathematical or logical problems. For example:

students = ["Alice", "Bob", "Charlie"]
witness = "Bob"
counterexample = "David"
is_witness = witness in students
is_counterexample = counterexample in students
print(is_witness) # True
print(is_counterexample) # False

In the above code, the Walrus operator is used to check if the witnesses and counterexamples are present in the list of students. This allows for a more compact and readable way of performing the check.

Walrus Operator Syntax

The Walrus operator has a simple syntax: :=. It can be used within expressions to assign values to variables. Here are a few examples of its usage:

x := 10
y := 2 * x + 1
is_even := x % 2 == 0

In the above code, the Walrus operator is used to assign the value 10 to the variable x, perform calculations using x, and check if x is even. This syntax eliminates the need for separate assignment statements and makes the code more concise.

Walrus Operator Pitfalls

While the Walrus operator can be a powerful tool, it is important to use it judiciously and be aware of a few potential pitfalls. Here are some key points to keep in mind:

  • Readability: The Walrus operator can make the code more concise, but it should not sacrifice readability. It is important to strike a balance between brevity and clarity.
  • Scope: Variables assigned using the Walrus operator have a limited scope. They are only accessible within the immediate enclosing scope. This should be considered when using the operator in nested expressions.
  • Precedence: The Walrus operator has a lower precedence than most other operators, such as arithmetic and comparison operators. This means that parentheses are often required to ensure correct evaluation order.
  • Backward Compatibility: The Walrus operator is only available in Python 3.8 and later versions. If you are working on a project that needs to support older Python versions, you will need to use alternative assignment methods.


The Walrus operator (:=) in Python 3.8 introduces a new syntax for assigning variables within expressions. It provides concise and readable code solutions for various use cases, such as debugging, working with lists and dictionaries, list comprehensions, while loops, and mathematical or logical problems.

By understanding the fundamentals, use cases, syntax, and potential pitfalls of the Walrus operator, you can leverage its power to write more efficient and elegant Python code. So go ahead, experiment with the Walrus operator, and enhance your Python programming skills!