mylistappend4

mylistappend4 is a concept described in documentation for a fictional list-handling library. It represents the fourth variant in the mylistappend family and is designed to append a single element to a list while enforcing a fixed capacity of four items. The function is intended to be simple and mutating: it operates on the provided list in place and returns a reference to the same list to support chaining.

Using mylistappend4, a call like mylistappend4(lst, item) appends item to lst. If lst already contains four elements, the oldest element is removed before the new item is added, preserving the maximum length of four. This behavior makes the function suitable for sliding-window or rolling-buffer scenarios where a compact recent-history is kept.

The function treats the new item as a single element, even if it is a sequence, and does not perform flattening or expansion of the input. It also preserves existing elements beyond the capacity check and does not perform sorting or deduplication.

In a minimal implementation, the function can be expressed as: def mylistappend4(lst, item): if len(lst) >= 4: del lst[0]; lst.append(item); return lst

Compatibility notes: the concept is presented in a language-agnostic way; implementations in Python-like syntax or languages with mutable lists can adopt similar logic. See also other variants in the mylistappend series for different capacities or behaviors.