List with empty indexes in python, how to remove?

Question

I am trying to remove a position from an empty list, as a simple example that demonstrates or is trying to remove.

#Test about fruits

fruits = []

fruits.append('maça')
fruits.append('goiaba')
fruits.append('uva')
fruits.append('pera')
fruits.append('bananna')
fruits[1] = []

print (fruits)

Output : ['maça', [], 'uva', 'pera', 'bananna']

Desired output ['maça', 'uva', 'pera', 'bananna']

Just remembering that it is a simple example, so I can apply it in a more robust program that I am developing that presents the same problem of having a "position" in the list with a 'null' or empty value in this case.

[`list(filter(None, fruits))`](https://docs.python.org/3/library/functions.html#filter) — Olvin Roght, Jan 27 '20 at 19:40
In this case your second element is an empty list, not an empty element, is that actually your case? — Juan C, Jan 27 '20 at 19:41
It would probably be a bit more pythonic to use `None` instead of `[]`, or to remove the item from the list immediately instead of using a sentinel. — 0x5453, Jan 27 '20 at 19:42
@JohnGordon it worked perfectly, thank you very much and everyone who responded as well. — Janio Carvalho, Jan 27 '20 at 19:46
How big is your list and how many empty lists can it contain? — Kelly Bundy, Jan 27 '20 at 19:51
Why are you doing `fruits[1] = []`? That is not how you remove an element from a list. To remove an element at an index, you use `del fruits[1]`, for example — juanpa.arrivillaga, Jan 27 '20 at 19:55
@juanpa.arrivillaga How so? I don't see any better way to do it, given that OP said "it is a simple example, so I can apply it in a more robust program" — John Gordon, Jan 27 '20 at 20:21
@PatrickArtner There is no (direct) list iteration, so I don't understand what problem you are pointing out. — John Gordon, Jan 27 '20 at 20:24
@JohnGordon because it is a quadratic-time algorithm. You can do it in linear time by using `fruits = [x for x in fruits if x == []]` or the in-place equivalent (probably not necessary) — juanpa.arrivillaga, Jan 27 '20 at 20:28

Barmar · Answer 1 · 2020-01-27T19:56:26.127

0

Use pop() to remove an element from a list by its index, rather than assigning an empty value to the index.

fruits.pop(1)

or del

del fruits[1]

pop() allows you to retrieve the value being removed at the same time.

edited Jan 27 '20 at 19:56

answered Jan 27 '20 at 19:52

Barmar

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score 0 · Answer 2 · answered Jan 27 '20 at 19:57

0

You can use

del fruits[1]

See Difference between del, remove and pop on lists for the differences.

answered Jan 27 '20 at 19:57

user0

185
11

Sorry, I hadn't seen the other answer had been edited. The link to the other question is still useful. – user0 Jan 27 '20 at 20:02

List with empty indexes in python, how to remove?

2 Answers2