Remove specific item in a list

Question

I'm trying to remove some specific '' in the list using python.

The list is [1,'','',2,'','','',3,'']. I want to remove just one '' between two values. which means the output I want is [1,'',2,'','',3]. The code I had shows as below:

for j in range (len(lst)):
    if len(lst[j]) == 1:
        lst.remove(lst[j+1])

I suggest that you build a new list rather than modifying the list that you iterate over. — Code-Apprentice, Jun 18 '19 at 16:48
This is a sample. The actual list is too big to manually build — Andy, Jun 18 '19 at 16:49
Is your question how to remove multiple blank strings from this list? — Yaakov Bressler, Jun 18 '19 at 16:51
Do you want to remove consecutive blanks or do you want to have one blank between each pair? — MisterMiyagi, Jun 18 '19 at 16:53
@andy The problem is that when you remove an element, the index on the next iteration is incorrect. If you really want to modify the existing list, you will need to take this into account and use a `while` loop instead of a `for`. — Code-Apprentice, Jun 18 '19 at 16:58

Andrej Kesely · Answer 1 · 2019-06-18T17:05:13.857

Using itertools.groupby:

from itertools import groupby

l = [1,'','',2,'','','',3,'']

new_list = []
for v, g in groupby(l):
    new_list += list(g) if v != '' else list(g)[:-1]

print(new_list)

Prints:

[1, '', 2, '', '', 3]

Version 2 (one-liner with itertools.chain):

from itertools import groupby, chain

l = [1,'','',2,'','','',3,'']
new_list = [*chain.from_iterable(list(g) if v != '' else list(g)[:-1] for v, g in groupby(l))]
print(new_list)

score 0 · Answer 2 · answered Jun 18 '19 at 16:51

0

You can use the del operator. Just provide the index. del lst[1].

answered Jun 18 '19 at 16:51

Ahmed

120
6

This will still run into problems with the index during iteration. – Code-Apprentice Jun 18 '19 at 16:54
1

yes. But it worked even with the index error! Why? – Andy Jun 18 '19 at 16:57

Remove specific item in a list

2 Answers2