Python @property decorator

In Python, a decorator feature wraps a function, appends several functionalities to existing code, and then returns it. Methods and functions are callable because they can be called. As a result, a decorator is a callable that returns a callable. This is also known as metaprogramming because a section of the programme changes another section of the programme at compile time. Note: For more information, see Decorators in Python.

Python @property decorator

@property decorator is a Python built-in decorator that allows you to define properties without having to call the inbuilt function property (). Which is used to return the property attributes of a class as parameters from the specified getter, setter, and deleter. Let’s look at some examples of how to use the @property decorator in Python: Exemplification 1:

# Python program to illustrate the use of
# @property decorator
# Defining class
class Portal:
# Defining __init__ method
def __init__(self):
self.__name =''
# Using @property decorator
@property
# Getter method
def name(self):
return self.__name
# Setter method
@name.setter
def name(self, val):
self.__name = val
# Deleter method
@name.deleter
def name(self):
del self.__name
# Creating object
p = Portal();
# Setting name
p.name = 'CarToon'
# Prints name
print (p.name)
# Deletes name
del p.name
# As name is deleted above this
# will throw an error
print (p.name)

Output:

CarToon
## An error is thrown
Traceback (most recent call last):
File "main.py", line 42, in
print (p.name)
File "main.py", line 16, in name
return self.__name
AttributeError: 'Portal' object has no attribute '_Portal__name'

The @property decorator is used here to define the property name in the class Portal, which has three methods (getter, setter, and deleter) with similar names, namely name(), but with different number of parameters. Whereas name(self) is a getter method and is labelled with @property, name(self, val) is a setter method because it is used to set the value of the attribute __name and is labelled with @name.setter. Finally, the method denoted by @name. deleter is a deleter method that can remove the value assigned by the setter method. However, deleter is called using the keyword del. Exemplification 2:

Python program to illustrate the use of
# @property decorator
# Creating class
class Celsius:
# Defining init method with its parameter
def __init__(self, temp = 0):
self._temperature = temp
# @property decorator
@property
# Getter method
def temp(self):
# Prints the assigned temperature value
print("The value of the temperature is: ")
return self._temperature
# Setter method
@temp.setter
def temp(self, val):
# If temperature is less than -273 than a value
# error is thrown
if val < -273:
raise ValueError("It is a value error.")
# Prints this if the value of the temperature is set
print("The value of the temperature is set.")
self._temperature = val
# Creating object for the stated class
cel = Celsius();
# Setting the temperature value
cel.temp = -270
# Prints the temperature that is set
print(cel.temp)
# Setting the temperature value to -300
# which is not possible so, an error is
# thrown
cel.temp = -300
print(cel.temp)

Output:

The value of the temperature is set.
The value of the temperature is:
-270
# An error is thrown
Traceback (most recent call last):
File "main.py", line 47, in
cel.temp = -300
File "main.py", line 28, in temp
raise ValueError("It is a value error.")
ValueError: It is a value error.

A value error is thrown here because the temperature assigned must be greater than -273. But it’s -300 degrees here. As a result, a value error is thrown.