Python property() function returns a property attribute. It’s mostly used to create a manageable class attribute.
Python property()
Python property() function syntax is:
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class property(fget=None, fset=None, fdel=None, doc=None) |
- fget: function for getting the attribute value
- fset: function to set the attribute value
- fdel: function to delete the attribute
- doc: creates the docstring for the attribute to be used in help() function.
Let’s look at an example to create property attribute in a class.
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class Person: def __init__(self): self._name = None def get_name(self): print('get_name called') return self._name def set_name(self, i): print('set_name called') self._name = i def del_name(self): print('del_name called') del self._name name = property(get_name, set_name, del_name, "Person's Name Attribute") d = Person() d.name="Pankaj" print(d.name) del d.name |
Output:
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set_name called get_name called Pankaj del_name called |
Notice that Person name property is managed through specified methods and it’s using the _name private property of Person.
We can create a read-only attribute or non-deletable attribute using property function.
If we define property function as:
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name = property(get_name, set_name, None) |
Then del d.name will throw exception as AttributeError: can't delete attribute.
Similarly, if we define property attribute as:
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name = property(get_name, None, None) |
The name will be read-only. If we try to set its value using d.name="Pankaj" then exception will be thrown as AttributeError: can't set attribute.
Python Property Decorator
We can use @property decorator to achieve the same thing.
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class Data: def __init__(self): self._id = None @property def id(self): print('id getter') return self._id @id.setter def id(self, i): print('id setter') self._id = i @id.deleter def id(self): print('id deleter') del self._id d = Data() d.id = 100 print(d.id) del d.id |
Output:
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id setter id getter 100 id deleter |
Reference: Official Documentation