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 OurBigBook.com, Jun 06 '17 at 12:59

score 108 · Accepted Answer · edited Aug 22 '21 at 18:27

108

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

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answered Sep 16 '16 at 23:32

mgilson

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5

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
@Manngo This does exactly what's asked and should be the accepted answer. (Though I don't know if, performance-wise, it's all same) – OverLordGoldDragon Jul 27 '23 at 19:49

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

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

score 1 · Answer 3 · answered Sep 16 '22 at 19:41

I'm not certain this question is still being followed but I recently wrote a short code that resembles what is being asked here. I was writing an interactive script to perform some analyses so I had a series of inputs serving to read in certain columns from a CSV:

X = input('X COLUMN NAME?:\n')
Y = input('Y COLUMN NAME?:\n')
Z = input('Z COLUMN NAME?:\n')
cols = [X,Y,Z]

Then, I brought the for-loop into 1 line to read into the desired index position:

[cols.insert(len(cols),x) for x in input('ENTER COLUMN NAMES (COMMA SEPARATED):\n').split(', ')]

This may not necessarily be as concise as it could be (I would love to know what might work even better!) but this might clean some of the code up.

corvus · Answer 4 · 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 0 · Answer 5 · answered Jan 20 '23 at 10:45

0

The python equivalent of JavaScript

myArray.splice(insertIndex, removeNElements, ...insertThese)

would be:

my_list[insert_index:insert_index + remove_n_elements] = insert_these

answered Jan 20 '23 at 10:45

Bjorkegeek

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Madhu Kumar · Answer 6 · 2023-03-10T16:32:32.233

0

Modifying the solution shared by RFV in earlier post.
Solution:
list1=list1[:position] + list2 + list1[position:]
    
Ex: Trying to insert the list of items at the 3rd index(2 is used in code snippet as positive indexing starts from 0 in Python)

list1=[0,1,23,345.22,True,"Data"] 
print(type(list1))
print(list1)
list2=[2,3,4,5]
list1=list1[:2] + list2 + list1[2:]
print("After insertion the values are",list1)
    
Ouput for the above code snippet.
<class 'list'>
[0, 1, 23, 345.22, True, 'Data']
After insertion the values are [0, 1, 2, 3, 4, 5, 23, 345.22, True, 'Data']

edited Mar 10 '23 at 16:32

answered Mar 10 '23 at 16:25

Madhu Kumar

1
1

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As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Mar 12 '23 at 17:03

score -1 · Answer 7 · 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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