Python property() function returns the object of the property class and it is used to create property of a class.
Syntax: property(fget, fset, fdel, doc)
Parameters:
- fget() – used to get the value of attribute
- fset() – used to set the value of attribute
- fdel() – used to delete the attribute value
- doc() – string that contains the documentation (docstring) for the attribute
Return: Returns a property attribute from the given getter, setter and deleter.
Note:
- If no arguments are given, property() method returns a base property attribute that doesn’t contain any getter, setter or deleter.
- If doc isn’t provided, property() method takes the docstring of the getter function.
Example #1: Using property() method
Python3
# Python program to explain property() function# Alphabet classclass Alphabet: def __init__(self, value): self._value = value # getting the values def getValue(self): print('Getting value') return self._value # setting the values def setValue(self, value): print('Setting value to ' + value) self._value = value # deleting the values def delValue(self): print('Deleting value') del self._value value = property(getValue, setValue, delValue, )# passing the valuex = Alphabet('Lazyroar')print(x.value)x.value = 'GfG'del x.value |
Output:
Getting value Lazyroar Setting value to GfG Deleting value
Python property Using Decorator
The main work of decorators is they are used to add functionality to the existing code. Also called metaprogramming, as a part of the program tries to modify another part of the program at compile time.
Example #2: Using @property decorator
Python3
# Python program to explain property()# function using decoratorclass Alphabet: def __init__(self, value): self._value = value # getting the values @property def value(self): print('Getting value') return self._value # setting the values @value.setter def value(self, value): print('Setting value to ' + value) self._value = value # deleting the values @value.deleter def value(self): print('Deleting value') del self._value# passing the valuex = Alphabet('Peter')print(x.value)x.value = 'Diesel'del x.value |
Output:
Getting value Peter Setting value to Diesel Deleting value
Using @property decorator works same as property() method.
First, specify that value() method is also an attribute of Alphabet then, we use the attribute value to specify the Python property setter and the deleter. Notice that the same method value() is used with different definitions for defining the getter, setter, and deleter. Whenever we use x.value, it internally calls the appropriate getter, setter, and deleter.
Python property vs attribute
Class Attribute: Class Attributes are unique to each class. Each instance of the class will have this attribute.
Python3
# declare a classclass Employee: # class attribute count = 0 # define a method def increase(self): Employee.count += 1# create an Employee# class objecta1 = Employee()# calling object's methoda1.increase()# print value of class attributeprint(a1.count)a2 = Employee()a2.increase()print(a2.count)print(Employee.count) |
Output:
1 2 2
In the above example, the count variable is a class attribute.
Python property(): Returns object of the property class
Python3
# create a classclass gfg: # constructor def __init__(self, value): self._value = value # getting the values def getter(self): print('Getting value') return self._value # setting the values def setter(self, value): print('Setting value to ' + value) self._value = value # deleting the values def deleter(self): print('Deleting value') del self._value # create a properties value = property(getter, setter, deleter, ) # create a gfg class objectx = gfg('Happy Coding!')print(x.value) x.value = 'Hey Coder!' # deleting the valuedel x.value |
Output:
Getting value Happy Coding! Setting value to Hey Coder! Deleting value
Applications
By using property() method, we can modify our class and implement the value constraint without any change required to the client code. So that the implementation is backward compatible.
