Hello again! In this article, we’ll be taking a look at Python property decorator.<\/p>\n\n\n\n
Python has a very useful feature called decorators, which is just a syntactic sugar for function-wrappers. Here, we’ll be focusing on the property decorator, which is a special type of decorator.<\/p>\n\n\n\n
This topic may be a bit confusing to you, so we’ll cover it step-by-step, using illustrative examples. Let’s get started!<\/p>\n\n\n\n
The Property decorator is based on the in-built You can call this in your Python Interpreter and take a look:<\/p>\n\n\n This The list of methods is given below:<\/p>\n\n\n\n But it does not stop there! These methods can be used on other objects too, and act as decorators themselves!<\/p>\n\n\n\n So, for example, we can use So, the thing to note is that the property decorator will use this function, which will have some special methods for reading and writing to the object. But how does that help us?<\/p>\n\n\n\n Let’s take a look now.<\/p>\n\n\n\n To use the property decorator, we need to wrap it around any function \/ method.<\/p>\n\n\n\n Here’s a simple example:<\/p>\n\n\n This is the same as:<\/p>\n\n\n So here, we wrap Let’s now take a simple example, by using the property decorator on a class method.<\/p>\n\n\n\n Consider the below class, without the any decorated methods:<\/p>\n\n\n Output<\/strong><\/p>\n\n\n Here, as you can see, when we only change the To ensure that the Output<\/strong><\/p>\n\n\n Here, we have solved our problem by converting However, this is not the best way to tackle this problem, since you may need to convert all such attributes into a method instead, and change the attributes into method calls. This is not convenient!<\/p>\n\n\n\n To reduce our pain, we can use the The idea is to make We can directly do this : Let’s try this out now!<\/p>\n\n\nproperty()<\/code> function. This function returns a special property<\/code> object.<\/p>\n\n\n\n\n>>> property()\n<property object at 0x000002BBD7302BD8>\n<\/pre><\/div>\n\n\n
property<\/code> object has some extra methods, for getting and setting the values of the object. It also has a method for deleting it.<\/p>\n\n\n\nproperty().getter<\/code><\/li>property().setter<\/code><\/li>property().deleter<\/code><\/li><\/ul>\n\n\n\nproperty().getter(obj)<\/code>, which will give us another property object!<\/p>\n\n\n\n
\n\n\n\nUsing the Python Property Decorator<\/h2>\n\n\n\n
\n@property\ndef fun(a, b):\n return a + b\n<\/pre><\/div>\n\n\n
\ndef fun(a, b):\n return a + b\n\nfun = property(fun)\n<\/pre><\/div>\n\n\n
property()<\/code> around fun()<\/code>, which is exactly what a decorator does!<\/p>\n\n\n\n\nclass Student():\n def __init__(self, name, id):\n self.name = name\n self.id = id\n self.full_id = self.name + " - " + str(self.id)\n\n def get_name(self):\n return self.name\n\ns = Student("Amit", 10)\nprint(s.name)\nprint(s.full_id)\n\n# Change only the name\ns.name = "Rahul"\nprint(s.name)\nprint(s.full_id)\n<\/pre><\/div>\n\n\n\nAmit\nAmit - 10\nRahul\nAmit - 10\n<\/pre><\/div>\n\n\n
name<\/code> attribute of our object, it’s reference to the full_id<\/code> attribute is still not updated!<\/p>\n\n\n\nfull_id<\/code> attribute also gets updated whenever name<\/code> or id<\/code> gets updated, one solution could be to make full_id<\/code> into a method instead.<\/p>\n\n\n\nclass Student():\n def __init__(self, name, id):\n self.name = name\n self.id = id\n\n def get_name(self):\n return self.name\n\n # Convert full_id into a method\n def full_id(self):\n return self.name + " - " + str(self.id)\n\ns = Student("Amit", 10)\nprint(s.name)\n# Method call\nprint(s.full_id())\n\ns.name = "Rahul"\nprint(s.name)\n# Method call\nprint(s.full_id())\n<\/pre><\/div>\n\n\n\nAmit\nAmit - 10\nRahul\nRahul - 10\n<\/pre><\/div>\n\n\n
full_id<\/code> into a method full_id()<\/code>.<\/p>\n\n\n\n@property<\/code> decorator instead!<\/p>\n\n\n\nfull_id()<\/code> into a method, but enclose it using @property<\/code>. This way, we would be able to update the full_id<\/code>, without having to treat it as a function call.<\/p>\n\n\n\ns.full_id<\/code>. Notice that there is no method call here. This is because of the property decorator.<\/p>\n\n\n\n\nclass Student():\n def __init__(self, name, id):\n self.name = name\n self.id = id\n\n def get_name(self):\n return self.name\n\n @property\n def full_id(self):\n return self.name + " - " + str(self.id)\n\ns = Student("Amit", 10)\nprint(s.name)\n# No more method calls!\nprint(s.full_id)\n\ns.name = "Rahul"\nprint(s.name)\n# No more method calls!\nprint(s.full_id)\n<\/pre><\/div>\n\n\n