del() vs del statement in python

Question

>>> li = [1, 2, 3, 4]
>>> li
[1, 2, 3, 4]
>>> del li[2] #case 1
>>> li
[1, 2, 4]
>>> del(li[2])  # case 2
>>> li
[1, 2]
>>> del (li[1]) # case 3
>>> li
[1]
>>>

One of my professors used case 2 to delete item from list.
As per python documentation case 1 is right and there is also another syntactic way exist from this answer so case 3 also right, but as per my knowledge there is no del method exist in python, how case 2 is valid. I searched whole python documentation but could not find it.

Update: if i write del method myself in my module and use case 2 at same time, how python interpreter differentiates between them or will it through an error, although i never tried until now

You can put parentheses in lots of places without affecting anything. Here they're simply redundant. Just like `return 1` is the same as `return (1)`. — khelwood, Nov 15 '18 at 15:32
okay, if i write del method in my module and use the above at same time, how python interpreter differentiates between the, although i never tried until now. — Srinivas, Nov 15 '18 at 15:34
Case 2 is not a function call, it is still a statement call. The same reason why `if(cond)` and `if (cond)` and `if cond` are all the same. — Gerges, Nov 15 '18 at 15:34
You should stick with `del ((((((((((((((((((((( list[0] ))))))))))))))))))))) ` ;) — Chris_Rands, Nov 15 '18 at 15:35
I never use del, I use `list.pop` also don't name your list `list` — Jean-François Fabre, Nov 15 '18 at 15:37
You *can't* write a `del` function in your module. `del` is a keyword. — khelwood, Nov 15 '18 at 15:37
If parenthesis are redundant in everywhere then why do i need for print() in python 3, just curious. — Srinivas, Nov 15 '18 at 15:43
If you define `lst = [1, 2, 3, 4]` after each Case you will get the same result. You'r deleting the same list. — Kian, Nov 15 '18 at 15:50
@Srinivas This is because `print` was changed from a statement (python 2) to a function (python 3). — Gerges, Nov 15 '18 at 15:50
Please do not use `list` as a variable name; you will overwrite the function by the same name and it is generally confusing. — dawg, Nov 15 '18 at 15:51
@dawg , is `list` is not a keyword in python, then why didn't i get an error? — Srinivas, Nov 15 '18 at 15:52
It is not a keyword. `list` is a function name that can be overwritten silently. — dawg, Nov 15 '18 at 15:53

Netwave · Answer 1 · 2018-11-15T15:38:06.273

11

All of them are the same, del is a keyword as yield or return, and (list[1]) evaluates to list[1]. So del(list[1]) and del (list[1]) are the same. For the base case, since you dont have the () you need to force the extra space, hence del list[1].

EDIT: You cannot redifine del since it is a language keyword.

edited Nov 15 '18 at 15:38

answered Nov 15 '18 at 15:32

Netwave

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score 1 · Answer 2 · answered Nov 15 '18 at 15:33

1

The parenthehis is not mandatory with keyword (like if or del), but can put some if you want.

it's exactly the same thing

answered Nov 15 '18 at 15:33

iElden

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del() vs del statement in python

2 Answers2