data structuresalgorithmsand code simplification sequence base class for objects that look like sequences inherits from containeriterableand sized and defines the abstract methods _getitem_ (and _len_ (also provides default implementation of _contains_ () _iter_ () _reversed_ ()index()and count(that are implemented using nothing but the _getitem_ (and _len_ (methods mutablesequence base class for mutable sequences inherits from sequence and adds the abstract methods _setitem_ (and _delitem_ (also provides default implementation of append()reverse()extend()pop()remove()and _iadd_ (set base class for objects that work like sets inherits from containeriterableand sized and defines the abstract methods _len_ () _iter_ ()and _contains_ (also provides default implementation of the set operators _le_ () _lt_ () _eq_ () _ne_ () _gt_ () _ge_ () _and_ () _or_ () _xor_ () _sub_ ()and isdisjoint(mutableset base class for mutable sets inherits from set and adds the abstract methods add(and discard(also provides default implementation of clear()pop()remove() _ior_ () _iand_ () _ixor_ ()and _isub_ (mapping base class for objects that support mapping (dictionarylookup inherits from sizediterableand container and defines the abstract methods _getitem_ () _len_ ()and _iter_ ( default implementation of _contains_ ()keys()items()values()get() _eq_ ()and _ne_ (is also provided mutablemapping base class for mutable mapping objects inherits from mapping and adds the abstract methods _setitem_ (and _delitem_ (an implementation of pop()popitem()clear()update()and setdefault(is also added mappingview base class for mapping views mapping view is an object that is used for accessing the internals of mapping object as set for examplea key view is set-like object that shows the keys in mapping see appendix "python for more details keysview base class for key view of mapping inherits from mappingview and set itemsview base class for item view of mapping inherits from mappingview and set valuesview base class for (keyitemview of mapping inherits from mappingview and set lib fl ff