How to insert multiple elements into a list?

Question

In JavaScript, I can use splice to insert an array of multiple elements in to an array: myArray.splice(insertIndex, removeNElements, ...insertThese).

But I can't seem to find a way to do something similar in Python without having concat lists. Is there such a way? (There is already a Q&A about inserting single items, rather than multiple.)

For example myList = [1, 2, 3] and I want to insert otherList = [4, 5, 6] by calling myList.someMethod(1, otherList) to get [1, 4, 5, 6, 2, 3]

@mgilson No, extend only adds to the end, right? I'd like to be able to insert it anywhere in the list as indicated by `insertIndex` — TheRealFakeNews, Sep 16 '16 at 23:30
@alfasin Nope, because that uses concatenation. Also the OP of that is asking for permutations. — TheRealFakeNews, Sep 16 '16 at 23:37
@AlanH the example in the question is exactly what that other question describes how to do: `mylist[0:1] + otherlist + mylist[2:]` — Nir Alfasi, Sep 16 '16 at 23:49
Disagree with duplicate. The other question wants to insert one given item into multiple unrelated locations https://stackoverflow.com/questions/2218238/inserting-values-into-specific-locations-in-a-list-in-python — Ciro Santilli Путлер Капут 六四事, Jun 06 '17 at 12:59

score 96 · Accepted Answer · edited Aug 22 '21 at 18:27

96

To extend a list, you just use list.extend. To insert elements from any iterable at an index, you can use slice assignment...

>>> a = list(range(10))
>>> a
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> a[5:5] = range(10, 13)
>>> a
[0, 1, 2, 3, 4, 10, 11, 12, 5, 6, 7, 8, 9]

edited Aug 22 '21 at 18:27

wjandrea

23,210
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answered Sep 16 '16 at 23:32

mgilson

283,004
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667

This does the job, but doesn’t answer the actual question directly. The answer should have been something like `myList[1:1] = otherList`. – Manngo Mar 26 '22 at 03:10

score 5 · Answer 2 · answered Sep 17 '16 at 03:26

5

Python lists do not have such a method. Here is helper function that takes two lists and places the second list into the first list at the specified position:

def insert_position(position, list1, list2):
    return list1[:position] + list2 + list1[position:]

answered Sep 17 '16 at 03:26

RFV

751
6
21

3

Note this returns a new list, unlike the insert method – Quantum7 Sep 06 '17 at 16:19

corvus · Answer 3 · 2020-08-08T16:03:13.567

The following accomplishes this while avoiding creation of a new list. However I still prefer @RFV5s method.

def insert_to_list(original_list, new_list, index):
    
    tmp_list = []
    
    # Remove everything following the insertion point
    while len(original_list) > index:
        tmp_list.append(original_list.pop())
    
    # Insert the new values
    original_list.extend(new_list)
    
    # Reattach the removed values
    original_list.extend(tmp_list[::-1])
    
    return original_list

Note that it's necessary to reverse the order of tmp_list because pop() gives up the values from original_list backwards from the end.

Why would you pop items and add them to another list one by one? — Alexander, May 24 '22 at 07:05

score -1 · Answer 4 · answered Feb 03 '21 at 10:15

-1

use listname.extend([val1,val2,val,etc])

answered Feb 03 '21 at 10:15

PRASHANTKUMAR ILAGER

1

Thank you for contributing an answer. Would you kindly edit your answer to to include an explanation of your code? That will help future readers better understand what is going on, and especially those members of the community who are new to the language and struggling to understand the concepts. – sta Feb 03 '21 at 10:38
Same solution as in Corvus' answer. – Eric Aya Feb 03 '21 at 12:23

How to insert multiple elements into a list?

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