CODEWITHSUNDEEP
pythonpython-3.xlistinsert
Krishnan Ravikumar
Krishnan Ravikumar

Reputation: 295

What does list.insert() in actually do in python?

I have code like this:

squares = []
for value in range(1, 5):
    squares.insert(value+1,value**2)

print(squares)
print(squares[0])
print(len(squares))

And the output is :

[1, 4, 9, 16]

1

4

So even if I ask python to insert '1' at index '2', it inserts at the first available index. So how does 'insert' makes the decision?

Upvotes: 1

Views: 2273

Answers (2)

x-caliver
x-caliver

Reputation: 31

Basically, it's similar to append, except that it allows you to insert a new item at any position in the list, as opposed to just at the end.

Upvotes: 0

Olivier Melançon
Olivier Melançon

Reputation: 22314

From the Python3 doc:

list.insert(i, x)

Insert an item at a given position. The first argument is the index of the element before which to insert, so a.insert(0, x) inserts at the front of the list, and a.insert(len(a), x) is equivalent to a.append(x).

What is not mentionned is that you can give an index that is out of range and Python will then append to the list.

If you dig into the Python implementation you find the following in the ins1 function that does the insertion:

if (where > n)
    where = n;

So basically Python will max out your index to the length of the list.

Upvotes: 2

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