Python 简明教程

Python - Static Methods

What is Python Static Method?

在 Python 中， static method 是一种无需调用任何实例的方法。它与类方法非常相似，但不同之处在于静态方法没有 − self 对象的引用或对类 − cls 的引用的强制参数。

In Python, a static method is a type of method that does not require any instance to be called. It is very similar to the class method but the difference is that the static method doesn’t have a mandatory argument like reference to the object − self or reference to the class − cls.

静态方法用于访问给定类中的静态字段。因为它们与类绑定，而不是与实例绑定，所以它们不能修改类的状态。

Static methods are used to access static fields of a given class. They cannot modify the state of a class since they are bound to the class, not instance.

How to Create Static Method in Python?

有两种方法可以创建 Python 静态方法 −

There are two ways to create Python static methods −

  1. Using staticmethod() Function

  2. Using @staticmethod Decorator

Using staticmethod() Function

Python 的名为 staticmethod() 的标准库函数用于创建静态方法。它接受一个方法作为参数，并将其转换成一个静态方法。

Python’s standard library function named staticmethod() is used to create a static method. It accepts a method as an argument and converts it into a static method.

Syntax

staticmethod(method)

Example

在下方的 Employee 类中，showcount() 方法转换成一个静态方法。现在可以通过其对象或类本身的引用来调用这个静态方法。

In the Employee class below, the showcount() method is converted into a static method. This static method can now be called by its object or reference of class itself.

class Employee:
   empCount = 0
   def __init__(self, name, age):
      self.__name = name
      self.__age = age
      Employee.empCount += 1

   # creating staticmethod
   def showcount():
      print (Employee.empCount)
      return
   counter = staticmethod(showcount)

e1 = Employee("Bhavana", 24)
e2 = Employee("Rajesh", 26)
e3 = Employee("John", 27)

e1.counter()
Employee.counter()

执行以上代码将打印以下结果 −

Executing the above code will print the following result −

3
3

Using @staticmethod Decorator

创建静态方法的第二种方法是使用 Python @staticmethod 装饰器。当我们对一个方法使用这个装饰器时，它向解释器指示指定方法是静态的。

The second way to create a static method is by using the Python @staticmethod decorator. When we use this decorator with a method it indicates to the Interpreter that the specified method is static.

Syntax

@staticmethod
def method_name():
   # your code

Example

以下示例中，我们使用 @staticmethod 装饰器创建一个静态方法。

In the following example, we are creating a static method using the @staticmethod decorator.

class Student:
   stdCount = 0
   def __init__(self, name, age):
      self.__name = name
      self.__age = age
      Student.stdCount += 1

   # creating staticmethod
   @staticmethod
   def showcount():
      print (Student.stdCount)

e1 = Student("Bhavana", 24)
e2 = Student("Rajesh", 26)
e3 = Student("John", 27)

print("Number of Students:")
Student.showcount()

运行以上代码将打印以下结果 −

Running the above code will print the following result −

Number of Students:
3

Advantages of Static Method

使用静态方法有许多优势，包括 -

There are several advantages of using static method, which includes −

  1. Since a static method cannot access class attributes, it can be used as a utility function to perform frequently re-used tasks.

  2. We can invoke this method using the class name. Hence, it eliminates the dependency on the instances.

  3. A static method is always predictable as its behavior remain unchanged regardless of the class state.

  4. We can declare a method as a static method to prevent overriding.