What is the name of this operator “ _ ” in Python?

Question

I was reading Hidden features of Python and I came across this answer.

Right from the post:

When using the interactive shell, "_" contains the value of the last printed item:

>>> range(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> _
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>>

What is the name of this operator ? I cannot find it on the document and I've never heard of it (as well as in other languages). Is it worth using it?

PS. I want to know its name because I want to see how the function is implemented and to search if other languages have this awesome function.

there was a post regarding this before: http://stackoverflow.com/questions/5893163/underscore-in-python Regards — LoBS, Apr 07 '13 at 21:01
related : [What's the meaning of '_' in python?](http://stackoverflow.com/questions/3967231/whats-the-meaning-of-in-python) — Ashwini Chaudhary, Apr 07 '13 at 21:02

score 12 · Accepted Answer · answered Apr 07 '13 at 20:58

12

It's neither an operator nor a function. It's a variable that automatically gets assigned the result of each expression executed by the shell.

answered Apr 07 '13 at 20:58

NPE

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Would this be shell-dependent? – Apr 07 '13 at 21:00
4

@Sancho python-shell dependent, yes. But basically everyone uses the same Python shell (and even the less common variants still tend to implement it). – Amber Apr 07 '13 at 21:02
@Sancho In IPython shell the default value of `_` is `""`. – Ashwini Chaudhary Apr 07 '13 at 21:04

score 3 · Answer 2 · edited May 23 '17 at 12:23

3

It looks like that character has a couple functions. It is used preceding global variables so they are not mixed in with regular variables. It can also be used in a loop as a throwaway to indicate that the variable is not going to be used.

In this case, underscore (_) when typed into the interpreter will return the value of the last executed statement.

For more info

What is the purpose of the single underscore "_" variable in Python?

What is the meaning of a single- and a double-underscore before an object name?

the underscore of python

edited May 23 '17 at 12:23

Community

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answered Apr 07 '13 at 21:01

jfa

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"*It is used preceding global variables so they are not mixed in with regular variables*". That is not "use" of a variable. – Apr 07 '13 at 21:03

What is the name of this operator “ _ ” in Python?

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