An\u00a0iterable<\/span><\/a>\u00a0which supports efficient element access using integer indices via the\u00a0 The\u00a0__getitem__()<\/span><\/code><\/a>\u00a0special method and defines a\u00a0__len__()<\/span><\/code><\/a>\u00a0method that returns the length of the sequence. Some built-in sequence types are\u00a0list<\/span><\/code><\/a>,\u00a0str<\/span><\/code><\/a>,\u00a0tuple<\/span><\/code><\/a>, and\u00a0bytes<\/span><\/code><\/a>. Note that\u00a0dict<\/span><\/code><\/a>\u00a0also supports\u00a0__getitem__()<\/span><\/code><\/a>\u00a0and\u00a0__len__()<\/span><\/code><\/a>, but is considered a mapping rather than a sequence because the lookups use arbitrary\u00a0immutable<\/span><\/a>\u00a0keys rather than integers.<\/p>\ncollections.abc.Sequence<\/span><\/code><\/a>\u00a0abstract base class defines a much richer interface that goes beyond just\u00a0__getitem__()<\/span><\/code><\/a>\u00a0and\u00a0__len__()<\/span><\/code><\/a>, adding\u00a0count()<\/span><\/code>,\u00a0index()<\/span><\/code>,\u00a0__contains__()<\/span><\/code><\/a>, and\u00a0__reversed__()<\/span><\/code><\/a>. Types that implement this expanded interface can be registered explicitly using\u00a0register()<\/span><\/code>.<\/p>\n