Insert multiple items into a list at once in python

Asked May 29 '16 at 17:58

Active May 29 '16 at 18:00

Viewed 30 times

What is a pythonic way for inserting multiple items into a list? Suppose I have :

a = [1,2,3]
b = ['a', 'b', 'c']

and I want b to be inserted into a, that is for example:

a = [1, 2, 'a', 'b', 'c', 3]

What I have done is:

a.insert(2,None)
a[2:3] = b

or also:

a = a[0:2] + b + a[2:]

The last approach seems nicer because it is just one line, but the problem is that I think a new list is created, and if the list is very large could be a performance issue.

On the other hand, the first approach doesn't seem very pythonic.

asked May 29 '16 at 17:58

nadapez

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You can use the extend()-method that is provided by the list-type. b.extend(a) for example would add the items of a to b. – Supahupe May 29 '16 at 18:00
@Supahupe but the OP wants the elements to be inserted in the middle of the list – Aswin Murugesh May 29 '16 at 18:00
@Supahupe I think the question is to insert the items in a specific place – roganjosh May 29 '16 at 18:00
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No need to insert a value first, just use an empty slice: `a[2:2] = b`. – Martijn Pieters May 29 '16 at 18:02
@Aswing Murugesh you are right that was not clear for me at first, thx – Supahupe May 29 '16 at 18:04
Martijn, I like your comment better than the linked answer. It addresses this issue directly. – hpaulj May 29 '16 at 18:32

Insert multiple items into a list at once in python

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