Question

Based on this older thread, it looks like the cost of list functions in Python is:

• Random access: O(1)
• Insertion/deletion to front: O(n)
• Insertion/deletion to back: O(1)

Can anyone confirm whether this is still true in Python 2.6/3.x?

Answer 1

Take a look here. It’s a PEP for a different kind of list. The version specified is 2.6/3.0.

Append (insertion to back) is O(1), while insertion (everywhere else) is O(n). So yes, it looks like this is still true.

Operation...Complexity
Copy........O(n) 
Append......O(1)
Insert......O(n) 
Get Item....O(1)
Set Item....O(1)
Del Item....O(n) 
Iteration...O(n)
Get Slice...O(k)
Del Slice...O(n)
Set Slice...O(n+k)
Extend......O(k) 
Sort........O(n log n)
Multiply....O(nk)