[Python-ideas] Operator for inserting an element into a list
mikhailwas at gmail.com
Tue Jun 12 14:08:22 EDT 2018
On Tue, Jun 12, 2018 at 7:42 PM, Clint Hepner <clint.hepner at gmail.com> wrote:
>> On 2018 Jun 12 , at 10:54 a, Mikhail V <mikhailwas at gmail.com> wrote:
>> I think it would be logical to have the insert operator for lists.
>> Similar to list extend operator += , it could use one of augmented
>> assignment operators, e,g, /=.
>> L = ["aa"]
>> L /= "bb"
>> -> ["bb", "aa"]
>> L /= [1,2]
>> -> [[1,2], "aa"]
> -1. There's not much about this that is logical, no matter how much
> you want an insertion operator. Even if L /= "bb" worked, then logically
> so should L = L / "bb". However, there is no sense in which L / "bb"
> by itself has any meaning, and what would L = L / "bb" mean?
> And finally, L /= x (and really, every other augmented operator) *already has* a meaning:
Hi Clint, (and others),
I must say it is misunderstanding due to my false examples,
that I have pasted in original post (I had 2 cloned texts in my text editor
and copied the wrong one). I have posted correction just 10 minutes after
the original post, see last post.
Sorry for confusion!
So the idea was about an insert/append operator.
Which would use augmented operator. The operator may be
/= or ^=. (I like ^= more, so I'll put here example with it).
L = [1,2,3]
L[0:0] ^= 0
L[0:0] ^= -1
-> [-1, 0, 1, 2, 3]
L ^= 4 (without index, it works as append() )
-> [-1, 0, 1, 2, 3, 4]
As for your question, what would:
List1[a:b] = List1[c:d] ^ var
mean? (is that what you have asked?)
Well, I think this would mean simply :
- first append var to List1[c:d] ,
- then replace the List1[a:b] part with the result.
So at least L ^= 4 would make sense as L = L ^ 4.
Actually current semantics of += for lists:
L += var
L = L + var
are different, so it seems to me they were not meant to be
>> Note that there is a trick to 'insert' an element with slicing syntax, e.g.:
>> L[0:0] = [[1,2]]
>> -> [[1,2], "aa"]
>> The trick is to put brackets around the element and so it works as insert().
>> Though additional brackets look really confusing for this purpose, so I don't
>> feel like using this seriously.
> It's no more confusing than co-opting an unrelated operator to do the same thing.
If the intention is to insert an element, indeed it is confusing, for
me at least:
L[0:0] = "bb"
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