Getting Started with decorators in Python

In python, everything is an object. So functons are also objects which can be passed around. A decorator is a function that receives a function and returns a function.

Use case 1

Without using decorator

Let's say we have two simple functions to add and multiply numbers.

This will print

6
5

Now lets say we want to print execution time in both these functions. We could do something like this

This will print

multiply_me took 2.00507378578
6
add_me took 2.00509095192
5

Here we are repeating our logic for logging execution time. This can be solved by using decorators.

With using decorator

Let's create a wrapper function called timeme that will do the following-

Receive the function as an argument
Execute the function
Log the execution time

Next we can decorate our functions using syntatic sugar like this

This is similar to the following

multiply_me = timeme(multiply_me)

add_me = timeme(add_me)

Lastly runnig the functions will be like

print(multiply_me(3, 2))

print(add_me(3, 2))

This will print

multiply_me took 2.00506806374
6
add_me took 2.00509810448
5

Use case 2

Without using decorator

Lets define a function which depends on type of argument.

We can invoke the function with different arguments.

process_data(set())

process_data("string")

process_data(123)

process_data(Dog("bowbow"))

This will print

Default executed set()
str executed string
int executed 123
Dog executed bowbow

With using decorator

This coding style becomes hard to read as the number of cases increases. We can use singledispatch decorator.

This will print the same result

Default executed set()
str executed string
int executed 123
Dog executed bowbow