Is "*_" an acceptable way to ignore arguments in Python?
python
Solution
`_` is just a variable like any other, but by convention it means that you don't intend to use that value, just declare and forget it.
[OrderedSet() for _ in xrange(n)]
builds a list of `n` empty ordered sets. `_` is the index, but is unused; `_` is commonly used as required, but unused, variable name (not only in Python). This is just a tricky Python idiom because there is no built-in syntax to do this.
It's not uncommon to see this in other languages (where `_` is a valid identifier). `_` often means a variable one's not interested in the value of, but which is needed for syntactic reasons.
Note that `_(...)` as a macro call has another conventional meaning, which comes from gettext, where one uses `_("string literal")` to indicate a string that needs localization.
A thread to read from ActivesState
I can not say about any problems, Python doesn't use it internally, it's just a variable, it is us who have to be careful.
Regarding the syntax of * and **: The names `*args` and `**kwargs` are only by convention, but there's no need not to use them.
def my_callbacK_handler(a, b, *_):
...
So what I understand if I see this function in your code by `_` idiom, that this function only uses `a` and `b` arguments in its working and will ignore others.
As you state: "`*_` to express no interest in any further arguments".
Problem
If I have a function/method that is an implementation of a callback for some framework, and do not care for any further arguments, it seems to be syntactically correct, and to not have pylint/IDE complaints to use `*_` to express no interest in any further arguments. The point I think is to express intent to both the tools, and other developers that these arguments are not currently relevant. To clarify what I mean: ``` def my_callbacK_handler(a, b, *_): ... ``` I've not seen this idiom used in the wild - is it common, are there examples and are there known problems with this? For those not familiar: `_` expresses the intent that I am not interested in that symbol - it is the Python "dummy" that is recognized by IDE's and linters.