Decorators

Decorators provide a way to modify functions using other functions.
This is ideal when you need to extend the functionality of functions that you don’t want to modify.

def decor(fun):
def wrap():
print("++++")
fun()
print("--------")
return wrap

def print_text():
print("Hello World!")

decorated = decor(print_text)
decorated()

We defined a function named decor that has a single parameter func. Inside decor, we defined a nested function named wrap. The wrap function will print a string, then call func(), and print another string. The decor function returns the wrap function as its result.
We could say that the variable decorated is a decorated version of print_text – it’s print_text plus something.
In fact, if we wrote a useful decorator we might want to replace print_text with the decorated version altogether so we always got our “plus something” version of print_text.
This is done by re-assigning the variable that contains our function:
print_text = decor(print_text)
print_text()
NOTE: Now print_text corresponds to our decorated version.

In our previous example, we decorated our function by replacing the variable containing the function with a wrapped version.

def print_text():
print("Hello world!")
print_text = decor(print_text)

This pattern can be used at any time, to wrap any function.
Python provides support to wrap a function in a decorator by pre-pending the function definition with a decorator name and the @ symbol.
If we are defining a function we can “decorate” it with the @ symbol like:

@decor
def print_text():
print("Hello world!")

This will have the same result as the above code.

Note: A single function can have multiple decorators.