[Python] Decorator
2 min readFeb 15, 2022
Basic usage
def decorator(func):
print("Register The Decorator")
def inner():
print("Inner")
func()
return inner
@decorator
def function():
print("Function")
if __name__ == "__main__":
# Register The Decorator
print("Call Function") # Call Function
function() # Inner
# Function- Decorator would setup if python file start to compile, even if the function not be called.
- Above code equal to decorator(function).
def decorator(func):
print("Register The Decorator")
def inner(x):
print(x + "_Inner")
func(x)
return inner
@decorator
def function(x):
print(x)
if __name__ == "__main__":
# Register The Decorator
print("Call Function") # Call Function
function("Function") # Function_Inner
# Function- Above code equal to decorator(function) with parameter x.
Multiple usage
def decorator1(func):
print("Register The Decorator1")
def inner1():
print("Inner1")
func()
return inner1
def decorator2(func):
print("Register The Decorator2")
def inner2():
print("Inner2")
func()
return inner2
@decorator1
@decorator2
def function():
print("Function")
if __name__ == "__main__":
# Register The Decorator2
# Register The Decorator1
print("Call Function") # Call Function
function() # Inner1
# Inner2
# Function- Above code equal to decorator1(decorator2(function)).
Parameter usage
def decorator_param(active = False):
print("Register The Decorator_Param")
def decorator(func):
print("Register The Decorator")
if active:
def inner():
print("Inner")
return inner
else:
return func
return decorator
@decorator_param(active = True)
def function():
print("Function")
if __name__ == "__main__":
# Register The Decorator_Param
# Register The Decorator
print("Call Function") # Call Function
function() # Inner- Use outside decorator to pass the parameter into inside decorator.
Class usage
class Decorator:
print("Register The Decorator")
def __init__(self, func):
self.f = func
def inner(self):
print("Inner")
@Decorator
def function():
print("Function")
if __name__ == "__main__":
# Register The Decorator
print("Call Function") # Call Function
function.f() # Function
function.inner() # Inner- The function will pass into the initializer in Decorator class.
- One of the ways for encapsulation.
