Python类初始化– Python __init __（）函数

Python类初始化 (Python class init)

Whenever a beginner starts learning the Python programming language, they come across something like __init__ which usually they don’t fully understand. In this lesson, we will try to understand the use of __init__ completely with good examples. Let’s get started.

每当初学者开始学习Python编程语言时，他们都会遇到诸如__init__东西，通常他们并不完全了解。 在本课程中，我们将通过良好的示例尝试完全理解__init__的用法。 让我们开始吧。

了解python类的初始化函数 (Understanding python class init function)

Let’s see a short code snippet and see what we’re trying to understand:

让我们看一个简短的代码片段，看看我们试图理解什么：

class Student(object):

    def __init__(self, something):
        print("Init called.")
        self.something = something

    def method(self):
        return self.something 

my_object = Student('Jetty')

What does the __init__ method do? Why is it necessary? Let’s find out.

__init__方法有什么作用？ 为什么有必要？ 让我们找出答案。

python init方法有什么作用？ (What does the python init method do?)

When a new instance of a python class is created, it is the __init__ method which is called and proves to be a very good place where we can modify the object after it has been created.

当创建一个新的python类实例时，将调用__init__方法，事实证明这是一个非常好的地方，我们可以在创建对象后修改该对象。

This means that when we create a new instance of the class like:

这意味着当我们创建类的新实例时，如下所示：

my_object = Student('Jetty')

In above snippet, when we called Student with ‘Jetty’ (which could be actually anything), it gets passed to the __init__ function as the argument, Jetty. Let’s try to run this script now:

在上面的代码片段中，当我们用“ Jetty”（实际上可以是任何东西）调用Student时，它将作为参数Jetty传递给__init__函数。 让我们尝试现在运行此脚本：

__init__是构造函数吗？ (Is __init__ the constructor?)

Actually yes. __init__ is an oop construct. __init__ is the constructor for a class. Just like mentioned above, the __init__ method is called as soon as the memory for the object is allocated. Let’s see what we did above in our snippet:

其实，是。 __init__是一个oop构造。 __init__是类的构造函数。 就像上面提到的那样，一旦分配了对象的内存，就会调用__init__方法。 让我们看看上面片段中的操作：

def __init__(self, something):
    self.something = something

Using self is important because if you don’t and implement your method like:

使用self很重要，因为如果您不这样做，则可以实现以下方法：

def __init__(self, something):
    _something = something

The something parameter would be stored in variables on the stack and would be discarded as soon as the __init__ method goes out of scope.

something参数将存储在堆栈中的变量中，并且当__init__方法超出范围时将被丢弃。

__init__如何与继承一起使用？ (How __init__ works with Inheritance?)

When we have a class inheriting from a superclass, __init__ method works the same way. Let us try to demonstrate what happens when we try to initialise a child class:

当我们有一个从超类继承的类时， __init__方法的工作方式相同。 让我们尝试演示在尝试初始化子类时会发生什么：

class User(object):
    def __init__(self, something):
        print("User Init called.")
        self.something = something

    def method(self):
        return self.something 

class Student(User):
    def __init__(self, something):
        User.__init__(self, something)
        print("Student Init called.")
        self.something = something

    def method(self):
        return self.something 

my_object = Student('Jetty')

In above code, when we initialised the Student object, this will be the output which is created when we ran the above program:

So, before the child class, the parent’s class init was called. You can control this by modifying the order in which the init is called for a parent or a child class. Read more at python inheritance.

在上面的代码中，当我们初始化Student对象时，这将是运行上述程序时创建的输出：

因此，在子类之前，将调用父类的init。 您可以通过修改父类或子类的init调用顺序来控制它。 在python继承中阅读更多内容。

结论 (Conclusion)

To summarise, python __init__ is what is called as a constructor in other OOPs languages such as C++ and Java. The basic idea behind this is, it a special method which is automatically called when an object of that Class is created.

总而言之，python __init__在其他OOP语言（例如C ++和Java）中称为构造函数。 这背后的基本思想是，它是一种特殊的方法，当创建该Class的对象时会自动调用该方法。

翻译自: https://www.journaldev.com/18397/python-class-init