python tutorial - Private Attributes And Methods - learn python - python programming
Private
In the context of class, private means the attributes are only available for the members of the class not for the outside of the class.
- Suppose we have the following class which has private attributes (__alias):
# p.py
class P:
def __init__(self, name, alias):
self.name = name # public
self.__alias = alias # private
def who(self):
print('name : ', self.name)
print('alias : ', self.__alias)click below button to copy the code. By Python tutorial team
We create an instance of class P, then trying to access its attributes whether it's public or private:
>>> from p import P
>>> x = P(name='Alex', alias='amen')
>>> x.name
'Alex'
>>> x.alias
Traceback (most recent call last):
File "", line 1, in
AttributeError: P instance has no attribute 'alias'click below button to copy the code. By Python tutorial team
- For public attribute name, we can access through an instance variable, but not for the private attribute alias. Even we try this:
>>> x.__alias
Traceback (most recent call last):
File "", line 1, in
AttributeError: P instance has no attribute '__alias'click below button to copy the code. By Python tutorial team
still we're not allowed to access it.
- But here is a magic want. One underscore('_') with the class name will do magic:
>>> x._P__alias
'amen'click below button to copy the code. By Python tutorial team
The the following call also works as expected:
>>> x.who()
('name : ', 'Alex')
('alias : ', 'amen')click below button to copy the code. By Python tutorial team
Private Methods
- We're going to use the same code as in the previous section but we'll add two methods: foo() and __foo() methods:
# p2.py
class P:
def __init__(self, name, alias):
self.name = name # public
self.__alias = alias # private
def who(self):
print('name : ', self.name)
print('alias : ', self.__alias)
def __foo(self): # private method
print('This is private method')
def foo(self): # public method
print('This is public method')
self.__foo()click below button to copy the code. By Python tutorial team
How can we use the private method. If we try:
>>> from p2 import P
>>> x = P('Alex', 'amem')
>>> x.__foo()
Traceback (most recent call last):
File "", line 1, in
AttributeError: P instance has no attribute '__foo'click below button to copy the code. By Python tutorial team
The right way of accessing private method is this:
>>> x._P__foo()
This is private methodclick below button to copy the code. By Python tutorial team
- Of course, calling private method via public will work as expected:
>>> x.foo()
This is public emthod
This is private method