问题:Python,创建对象

我正在尝试学习python,现在我试图摆脱类的困扰,以及如何使用实例操纵它们。

我似乎无法理解这个练习问题:

创建并返回其名称,年龄和专业与输入相同的学生对象

def make_student(name, age, major)

我只是不了解对象的含义,是否意味着我应该在包含这些值的函数内创建一个数组?或创建一个类,让该函数位于其中,并分配实例?(在问这个问题之前,我被要求开设一个学生班,里面要说姓名,年龄和专业)

class Student:
    name = "Unknown name"
    age = 0
    major = "Unknown major"

I’m trying to learn python and I now I am trying to get the hang of classes and how to manipulate them with instances.

I can’t seem to understand this practice problem:

Create and return a student object whose name, age, and major are the same as those given as input

def make_student(name, age, major)

I just don’t get what it means by object, do they mean I should create an array inside the function that holds these values? or create a class and let this function be inside it, and assign instances? (before this question i was asked to set up a student class with name, age, and major inside)

class Student:
    name = "Unknown name"
    age = 0
    major = "Unknown major"

回答 0

class Student(object):
    name = ""
    age = 0
    major = ""

    # The class "constructor" - It's actually an initializer 
    def __init__(self, name, age, major):
        self.name = name
        self.age = age
        self.major = major

def make_student(name, age, major):
    student = Student(name, age, major)
    return student

请注意,即使Python哲学中的原则之一是“应该有一个,最好只有一个,这是显而易见的方式”,但仍然有多种方式可以做到这一点。您还可以使用以下两个代码段来利用Python的动态功能:

class Student(object):
    name = ""
    age = 0
    major = ""

def make_student(name, age, major):
    student = Student()
    student.name = name
    student.age = age
    student.major = major
    # Note: I didn't need to create a variable in the class definition before doing this.
    student.gpa = float(4.0)
    return student

我更喜欢前者,但在某些情况下后者可能有用–一种是在使用文档数据库(如MongoDB)时。

class Student(object):
    name = ""
    age = 0
    major = ""

    # The class "constructor" - It's actually an initializer 
    def __init__(self, name, age, major):
        self.name = name
        self.age = age
        self.major = major

def make_student(name, age, major):
    student = Student(name, age, major)
    return student

Note that even though one of the principles in Python’s philosophy is “there should be one—and preferably only one—obvious way to do it”, there are still multiple ways to do this. You can also use the two following snippets of code to take advantage of Python’s dynamic capabilities:

class Student(object):
    name = ""
    age = 0
    major = ""

def make_student(name, age, major):
    student = Student()
    student.name = name
    student.age = age
    student.major = major
    # Note: I didn't need to create a variable in the class definition before doing this.
    student.gpa = float(4.0)
    return student

I prefer the former, but there are instances where the latter can be useful – one being when working with document databases like MongoDB.


回答 1

创建一个类并为其提供__init__方法:

class Student:
    def __init__(self, name, age, major):
        self.name = name
        self.age = age
        self.major = major

    def is_old(self):
        return self.age > 100

现在,您可以初始化Student该类的实例:

>>> s = Student('John', 88, None)
>>> s.name
    'John'
>>> s.age
    88

尽管我不知道make_student如果做与相同的功能为什么为什么需要一个学生函数Student.__init__

Create a class and give it an __init__ method:

class Student:
    def __init__(self, name, age, major):
        self.name = name
        self.age = age
        self.major = major

    def is_old(self):
        return self.age > 100

Now, you can initialize an instance of the Student class:

>>> s = Student('John', 88, None)
>>> s.name
    'John'
>>> s.age
    88

Although I’m not sure why you need a make_student student function if it does the same thing as Student.__init__.


回答 2

对象是类的实例。类只是对象的蓝图。因此,根据您的类定义-

# Note the added (object) - this is the preferred way of creating new classes
class Student(object):
    name = "Unknown name"
    age = 0
    major = "Unknown major"

您可以make_student通过将属性明确分配给Student– 的新实例来创建函数

def make_student(name, age, major):
    student = Student()
    student.name = name
    student.age = age
    student.major = major
    return student

但是在构造函数(__init__)中执行此操作可能更有意义-

class Student(object):
    def __init__(self, name="Unknown name", age=0, major="Unknown major"):
        self.name = name
        self.age = age
        self.major = major

使用时会调用构造函数Student()。它将采用__init__方法中定义的参数。现在,构造函数签名实际上将是Student(name, age, major)

如果使用该make_student函数,那么函数是微不足道的(并且是多余的)-

def make_student(name, age, major):
    return Student(name, age, major)

为了好玩,这里有一个示例,说明如何在make_student不定义类的情况下创建函数。请不要在家尝试。

def make_student(name, age, major):
    return type('Student', (object,),
                {'name': name, 'age': age, 'major': major})()

Objects are instances of classes. Classes are just the blueprints for objects. So given your class definition –

# Note the added (object) - this is the preferred way of creating new classes
class Student(object):
    name = "Unknown name"
    age = 0
    major = "Unknown major"

You can create a make_student function by explicitly assigning the attributes to a new instance of Student

def make_student(name, age, major):
    student = Student()
    student.name = name
    student.age = age
    student.major = major
    return student

But it probably makes more sense to do this in a constructor (__init__) –

class Student(object):
    def __init__(self, name="Unknown name", age=0, major="Unknown major"):
        self.name = name
        self.age = age
        self.major = major

The constructor is called when you use Student(). It will take the arguments defined in the __init__ method. The constructor signature would now essentially be Student(name, age, major).

If you use that, then a make_student function is trivial (and superfluous) –

def make_student(name, age, major):
    return Student(name, age, major)

For fun, here is an example of how to create a make_student function without defining a class. Please do not try this at home.

def make_student(name, age, major):
    return type('Student', (object,),
                {'name': name, 'age': age, 'major': major})()

回答 3

使用predefine类创建对象时,首先要创建一个用于存储该对象的变量。然后,您可以创建对象并存储您创建的变量。

class Student:
     def __init__(self):

# creating an object....

   student1=Student()

实际上,此init方法是class的构造方法。您可以使用一些属性来初始化该方法。在这一点上,创建对象时,您将必须为特定属性传递一些值。

class Student:
      def __init__(self,name,age):
            self.name=value
            self.age=value

 # creating an object.......

     student2=Student("smith",25)

when you create an object using predefine class, at first you want to create a variable for storing that object. Then you can create object and store variable that you created.

class Student:
     def __init__(self):

# creating an object....

   student1=Student()

Actually this init method is the constructor of class.you can initialize that method using some attributes.. In that point , when you creating an object , you will have to pass some values for particular attributes..

class Student:
      def __init__(self,name,age):
            self.name=value
            self.age=value

 # creating an object.......

     student2=Student("smith",25)

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