类返回语句不打印任何输出 [英] Class return statement not printing any output

问题描述

我正在学习类，并且 return 语句有问题（这是一条语句吗？希望如此），程序什么也不会输出，只是

I'm learning about Classes and am having a problem with the return statement (is it a statement? I hope so), the program prints out nothing, it just ends without doing anything.

class className:
    def createName(self, name):
        self.name = name
    def displayName(self):
        return self.name
    def saying(self):
        print("Hello %s" % self.name)

first = className()
second = className()

first.createName("Jack")
second.createName("Joy")

first.displayName()
second.displayName()

我知道我正在做的事情显然很错，但是我真的不知道该怎么办。谢谢您的帮助。

I know I'm doing something so obviously wrong but I really don't know what. I'd appreciate some help.

推荐答案

回答您的问题-返回不会打印任何内容，但会有些混乱，因为交互式python提示符会打印出最后一条语句的值，例如：

To answer your question - return does not print anything, but it is slightly confusing, since the interactive python prompt does print out the value of the last statement e.g.:

Python 2.7.2 (default, Jun 20 2012, 16:23:33) 
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 1+1
2

但是如果创建的文件内容为 1 + 1 并将其作为python脚本运行，什么也不会打印。

But if you create a file with contents 1+1 and run it as a python script, nothing is printed.

由于您说自己是新手，所以我会

Since you say that you are a newbie, I'll give you a few pointers on how to improve your code.

class className:
    def createName(self, name):
        self.name = name
    def displayName(self):
        return self.name
    def saying(self):
        print("Hello %s" % self.name)

className 具有冗余性，您应该将您的课程重命名为名称-还要 新样式 类应该始终继承 object ，所以让我们稍微更改一下定义：

className has redundancy, you should rename your class just Name - also new style classes should always inherit object, so let's change your definition a bit:

class Name(object):
    def createName(self, name):
        self.name = name
    def displayName(self):
        return self.name
    def saying(self):
        print("Hello %s" % self.name)

创建通过覆盖类 __ init __（）方法自动完成。例如：

Creating something is done automatically by overriding the classes __init__() method. e.g:

class Name(object):
    def __init__(self, name):
        self.name = name
    def displayName(self):
        return self.name
    def saying(self):
        print("Hello %s" % self.name)

这样，当您实例化您的班级时，例如，

this way you can already initialize your name when instantiating your class, e.g.

first = Name("Jack")

第二，显示是通过覆盖方法 __ repr __ 来惯用的，例如

Second, display is handled idiomatically by overriding the method __repr__ e.g.

class Name(object):
    def __init__(self, name):
        self.name = name
    def __repr__(self):
       return self.name
    def saying(self):
        print("Hello %s" % self.name)

这样，您只需要做两件事：

This way, you only need to do two things:

>>> n = Name("Jack")
>>> print n
Jack

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