DAY 3. static methods, class methods, properties, methods, examples of the method
There are four methods, instance methods, class methods, static methods, properties, methods
- Examples of methods
The first parameter is an instance method self, he would point to an instance of an object class, it can only be called an object, such as
class Demo:
def instanceMethod(self):
print("this is a instance method")
if __name__ == "__main__":
demo = Demo()
demo.instanceMethod()
When the incoming call does not need to point the object with the parameters, Python will call object instance method as the first parameter passed example of a method equivalent to
if __name__ == '__main__':
demo = Demo()
Demo.instanceMethod(demo)
- Class Methods
Use decorator @classmethod. The first argument must be a class object is the current, this parameter is generally agreed to name "cls", may be used (e.g. of Cf ()) or an instance (e.g., C (). F ()) calling a class method. In addition to the classes, the instance is ignored. If the derived class call the class method, the derived class object is passed as the first argument implied.
class Demo:
@classmethod
def classMethod(self):
print("this is a class method")
if __name__ == "__main__":
demo = Demo()
Demo.classMethod()
demo.classMethod()
Also syntactic sugar, the class or object will automatically call the class method as the first argument is invoked with the point
- Static method
Methods @staticmethod decorated with no self parameter called static method, static method does not receive an implicit first parameter, c ++ static method is similar, but takes up the namespace classes, no contact with the class, the a class name or object name calling
- Properties Methods
The method used to become a static property, use decorator@property
class C:
def __init__(self):
self._x = None
@property
def x(self):
"""I'm the 'x' property."""
return self._x
@x.setter
def x(self, value):
self._x = value
@x.deleter
def x(self):
del self._x
TODO: a bit difficult to learn another day special
to sum up
| method | Decorator | transfer | Usage scenarios (personal understanding) |
|---|---|---|---|
| Examples of methods | / | It can only be called an object | Most scenes |
| Class Methods | @classmethod | Object or class can be invoked | Operate only class attribute |
| Static method | @staticmethod | Object or class can be invoked | It does not operate in the class attributes and methods |
| Properties Methods | @property | By calling the static method attribute (without brackets) | EVERYTHING |
Reference article
GitHub face questions about python
Python static methods, class methods, properties, methods
Python object-oriented method, class methods, properties, methods
Python distinguished role instance method, class methods, static methods
