Python functools cached_property() Function

The Python cached_property() function transforms a method of a class into a property, where its value is computed only once and this value will be cached as a normal attribute. Here, the result is stored when the method is executed for the first time.

This function improves the performance of a program by avoiding the duplicate calculations and simplifies code by allowing method.

Syntax

Following is the syntax for the function.

@cached_property()

Parameters

This function doesn't accept any parameters.

Return Value

Decorator returns the cached result from the decorated method.

Example 1

In this example, we are calculating the area of a circle using the cached_property() decorator. The result is cached, so subsequent accesses to the area returns the cached value without recalculating.

from functools import cached_property
class Circle:
    def __init__(self, rad):
        self.rad = rad
    @cached_property
    def area(self):
        print("Calculating area of a circle.")
        return 3.14159 * self.rad ** 2
circle = Circle(23)
print(circle.area) 
print(circle.area)

Output

The result is generated as follows −

Calculating area of a circle.
1661.90111
1661.90111

Example 2

Now, we compute the total_sum of the numbers using the cached_property function. This result will be stored, so future accesses to total_sum retrieves the cached value without recalculating.

from functools import cached_property
class NumSeries:
    def __init__(self, num):
        self.num = num
    @cached_property
    def total_sum(self):
        print("Sum of the numbers")
        return sum(self.num)
series = NumSeries([21, 3, 12, 45, 65])
print(series.total_sum)  
print(series.total_sum)

Output

The code is generated as follows −

Sum of the numbers
146
146

Example 3

In the below code, the cached_property() decorator is used to cache the result of the function, converting the lowercase letters to uppercase.

from functools import cached_property
class MyString:
    def __init__(self, text):
        self.text = text
    @cached_property
    def upper_text(self):
        return self.text.upper()
s = MyString("welcome to tutorialspoint")
print(s.upper_text) 
print(s.upper_text)

Output

The output is obtained as follows −

WELCOME TO TUTORIALSPOINT
WELCOME TO TUTORIALSPOINT