变量分配给最后执行的行? [英] Variable assigned to the last executed line?

问题描述

我刚刚在Python解释器中发现了一些奇怪的东西.让我告诉你:

I just found something weird in the Python interpreter. Let me show you:

$ python
Python 2.7.1+ (r271:86832, Apr 11 2011, 18:13:53) 
[GCC 4.5.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> _
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name '_' is not defined
>>> 5 + 4
9
>>> _
9
>>> 'Hello world'
'Hello world'
>>> _
'Hello world'
>>> type(3.5)
<type 'float'>
>>> _
<type 'float'>

您可以在口译员中尝试此操作；这里没有技巧在工作！

You can try this in your interpreter; there are no tricks at work here!

最后执行的行的结果是否分配给名为_的变量?

Is the result of the last executed line being assigned to a variable named _?

有人知道吗?是否有任何相关文档?在什么情况下有用?

Does anybody know something about it? Is there any documentation about it? In which situation could it be useful?

推荐答案

在这里看看保留的标识符python .

特殊标识符_在交互式解释器中用于 存储上一次评估的结果；它存储在 内置模块.

The special identifier _ is used in the interactive interpreter to store the result of the last evaluation; it is stored in the builtin module.

此行为也可以在haskell的交互式环境ghci中找到.在这里使用it代替_.

This behavior can be found on haskell's interactive environment ghci also. Here instead of _ use it.

Prelude> 2+2
4
Prelude> it
4

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