List manipulation

Adds an element at a specific index in a list.

Data processing: inserting a new record into a sorted list at its correct position; User interface: adding a placeholder item at the beginning of a menu list

Common in scripts that maintain ordered collections, algorithms that build lists incrementally, or UI code that manages dynamic lists.

lst.insert(pos, item)

lst.insert(... , ...)

lst: list variable, pos: integer index, item: any object to insert

• Often used with len(lst) to append at end
• or with slicing
• or within loops that build lists.

• lst[pos:pos] = [item] or lst = lst[:pos] + [item] + lst[pos:]

Using an index out of range (raises IndexError), confusing insert with append, or expecting a return value (insert returns None).

append (adds to end), extend (adds iterable), slice assignment for multiple insertions.

Coming from Java’s ArrayList.add(index, element): similar but note Python’s list.insert modifies in place and returns None.

• list.append
• list.extend
• list.pop
• list.remove

Insert has O(n) time complexity due to shifting elements; if index > len(lst) it inserts at the end; the method returns None.

Allows precise ordering of elements without rebuilding the list.

Think 'insert at position' like putting a card into a deck at a specific spot.

Insert modifies the list in place and returns None; attempting to use its return value will result in None.

Use slice assignment for bulk inserts or collections.deque for efficient front inserts.