问题描述
我正在学习 Python 中的绳索.当我尝试使用 print()
函数打印 Foobar
类的对象时,我得到类似的输出这个:
I am learning the ropes in Python. When I try to print an object of class Foobar
using the print()
function, I get an output like this:
<__main__.Foobar instance at 0x7ff2a18c>
有没有办法设置类及其对象打印行为(或字符串表示)/em>?例如,当我在类对象上调用 print()
时,我想以某种格式打印其数据成员.如何在 Python 中实现这一点?
Is there a way I can set the printing behaviour (or the string representation) of a class and its objects? For instance, when I call print()
on a class object, I would like to print its data members in a certain format. How to achieve this in Python?
如果您熟悉 C++ 类,则可以通过添加 friend ostream& 为标准
ostream
实现上述功能.运算符< 类的方法.
If you are familiar with C++ classes, the above can be achieved for the standard
ostream
by adding a friend ostream& operator << (ostream&, const Foobar&)
method for the class.
推荐答案
>>> class Test:
... def __repr__(self):
... return "Test()"
... def __str__(self):
... return "member of Test"
...
>>> t = Test()
>>> t
Test()
>>> print(t)
member of Test
__str__
方法是什么打印时会发生调用,__repr__
方法是使用 repr()
时发生的情况 函数(或者当您使用交互式提示查看它时).
The
__str__
method is what gets called happens when you print it, and the __repr__
method is what happens when you use the repr()
function (or when you look at it with the interactive prompt).
如果没有给出
__str__
方法,Python 将打印 __repr__
的结果.如果你定义了 __str__
而不是 __repr__
,Python 将使用你在上面看到的 __repr__
,但仍然使用 __str__
用于打印.
If no
__str__
method is given, Python will print the result of __repr__
instead. If you define __str__
but not __repr__
, Python will use what you see above as the __repr__
, but still use __str__
for printing.
这篇关于如何使用print() 打印类的实例?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!