How can I remove specific index from list in python

Question

I'm trying to figure out how to remove specific index from list, but I don't know how to fix my problem. Can someone help me to solve this?

First, I have to get some numbers from users using input.

numbers = int(input("input any numbers: "))
list_num = list(numbers)

Second, if list_num[0] == 1, remove that element.

Third, if list_num[i+1] == list_num[i], remove list_num[i+1].

So, if the initial list goes like this: list_num = [1,2,7,8,13,20,21],

the final list will be list_num = [2,7,13,20]

This is the program to be fixed:

 numbers = int(input("input any numbers:"))
 list_num = list(numbers)
 if list_num[0] ==1:
    list_num.remove(num[0])
 for i in range(1,len(list_num)-1, 1):
    if list_num[i] = list_num[i+1] -1:
         list_num.remove(num[i+1])
 print(list_num)

Note that removing an item from a list whilst iterating through it will cause problems. It is best to use a list comprehension, or some other method to build a new list with elements from the old one. See [this](http://stackoverflow.com/questions/1207406/remove-items-from-a-list-while-iterating-in-python) question. — SiHa, Jun 07 '16 at 07:34
Just for fun: `print([item[0] for item in (list(x) for _, x in itertools.groupby(list_num, lambda v, c=itertools.count(): v - next(c)))])` :-) — Matthias, Jun 07 '16 at 08:48
Thank you for all of the comments, and I edited my question to be more organized. :) — jay0904, Jun 07 '16 at 09:32

Hassan Mehmood · Answer 1 · 2016-06-07T07:28:11.593

4

You can delete it by using keyword del. Here is the example.

my_list = [1, 2, 3, 4, 5]
del my_list[0] # 0 is the index

This will delete the first index of my_list. So the resultant list will be [2, 3, 4, 5]

Here is the section from the tutorial.

edited Jun 07 '16 at 07:28

answered Jun 07 '16 at 07:22

Hassan Mehmood

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score 1 · Accepted Answer · edited Jun 07 '16 at 08:14

Please review your question again. Please correct your question because it is unclear what you are trying to achieve. These are the two conditions that i think you wish to achieve.

if list[0] == 1 then remove that element.
if list[i+1]-1 == list[i] then remove list[i+1]

First of all in line 6 of your code there is an error, it should be if == and not if =.The following code will achieve the above conditions.

numbers = int(input("Enter the limit for the list : "))

list_num = []

for i in range(0,numbers):
    list_num.append(int(input("list["+str(i)+"]: ")))

if list_num[0] == 1:
    list_num.remove(list_num[0])
try:
    for i in range(0,len(list_num)):
        if list_num[i] == list_num[i+1]-1:
            list_num.remove(list_num[i+1])
except:
    print list_num

Input: [1,2,7,8,13,20,21]

Output: [2,7,13,20]

`list[i+1]-1 == list[i]`. Nice catch. – Matthias Jun 07 '16 at 08:25 — Matthias, Jun 07 '16 at 08:25

score -1 · Answer 3 · answered Jun 07 '16 at 07:57

There were several issues with your code including syntax, indentation and logic. I have formatted your code into a working manner. Good Luck.

numbers = input("input any numbers:")
list_num = list(numbers)

ret = []
for i,v in enumerate(list_num):
    if i == 0 and v == 1:
        continue
    if v == list_num[-1]:
        ret.append(v)
        break
    if v != list_num[i+1]:
        print v, list_num[i+1]
        ret.append(v)

print(ret)

How can I remove specific index from list in python

3 Answers3