delitem

Delitem refers to the operation of removing an item from a container by key or index, typically implemented through a language’s delete mechanism or a specialized method. It is often invoked when code needs to remove an element from a collection without returning a value.

In Python, the del statement triggers the __delitem__(self, key) method on objects that implement the mutable mapping or sequence protocol. The expression del obj[key] deletes the item associated with the given key or index. For lists, this removes the element at that position and shifts subsequent elements; for dictionaries, it removes the mapping with that key. Some containers support slice deletion, such as del a[2:5], which deletes a range. If the key or index is not present, a KeyError or IndexError is raised, and attempting to delete an unsupported key type raises TypeError.

Delitem is often contrasted with pop: del deletes without returning a value, while pop returns the removed value and can supply a default for missing keys in some languages. Custom containers can implement __delitem__ to define tailored deletion behavior, which is important for maintaining invariants or releasing resources.

Performance characteristics depend on the container. Deleting from lists typically has O(n) time due to element shifting, whereas deleting from dictionaries generally has O(1) average time. Implementations vary across languages, but the core idea remains: identify the targeted item and remove it from the container, updating internal structure as needed.

Beyond Python, many languages offer analogous concepts. For example, JavaScript provides a delete operator to remove object properties, while other languages expose erase or remove methods on container types. Delitem remains a foundational operation in managing dynamic collections.