The Walrus Operator in Python: What, Why, and How to Use It
If you are learning Python, you might have come across the term Walrus Operator. And if you don't know about it, don't worry. You can learn it from here.
#### What is the Walrus Operator?
The walrus operator (:=) was introduced in Python 3.8. Its official name is the “assignment expression.” It looks like a walrus face (:=), which is how it got its nickname. The walrus operator allows you to assign a value to a variable as part of an expression.
#### Why Use the Walrus Operator?
The walrus operator can make your code shorter and sometimes more readable. It lets you combine an assignment and a return value in one line. This can be handy in loops, comprehensions, and certain conditions.
#### How to Use the Walrus Operator
Let’s dive into some examples to see how it works and why you might use it.
##### Example 1: Using the Walrus Operator in a Loop
Imagine you want to read lines from a file until you find a specific line. Without the walrus operator, you’d write:
python
# Without walrus operator
file = open('bytecodex.txt', 'r')
line = file.readline()
while line:
print(line)
line = file.readline()
file.close()
With the walrus operator, you can simplify this:
python
# With walrus operator
file = open('bytecodex.txt', 'r')
while (line := file.readline()):
print(line)
file.close()
In the second example, line := file.readline() reads the line and assigns it to line, and the loop continues as long as line is not empty.
##### Example 2: Using the Walrus Operator in List Comprehensions
You can also use the walrus operator in list comprehensions to filter and transform data in a single line:
python
# Without walrus operator
values = [int(x) for x in input().split()]
squares = [x**2 for x in values if x > 10]
# With walrus operator
squares = [y**2 for x in input().split() if (y := int(x)) > 10]
Here, (y := int(x)) converts x to an integer and assigns it to y if y is greater than 10. Then, the square of y is added to the squares list.
##### Example 3: Simplifying Conditionals
Consider a scenario where you want to check and use a value from a function:
python
# Without walrus operator
match = re.search(pattern, text)
if match:
print(f"Found: {match.group(0)}")
# With walrus operator
if match := re.search(pattern, text):
print(f"Found: {match.group(0)}")
The walrus operator makes the code cleaner by combining the assignment and condition.