operation name indexing concatenation repetition membership length slicing operator in len explanation access an element of sequence combine sequences together concatenate repeated number of times ask whether an item is in sequence ask the number of items in the sequence extract part of sequence table operations on any sequence in python built-in collection data types in addition to the numeric and boolean classespython has number of very powerful builtin collection classes listsstringsand tuples are ordered collections that are very similar in general structure but have specific differences that must be understood for them to be used properly sets and dictionaries are unordered collections list is an ordered collection of zero or more references to python data objects lists are written as comma-delimited values enclosed in square brackets the empty list is simply lists are heterogeneousmeaning that the data objects need not all be from the same class and the collection can be assigned to variable as below the following fragment shows variety of python data objects in list [ , ,true, [ true my_list [ , ,true, my_list [ true note that when python evaluates listthe list itself is returned howeverin order to remember the list for later processingits reference needs to be assigned to variable since lists are considered to be sequentially orderedthey support number of operations that can be applied to any python sequence table reviews these operations and the following session gives examples of their use note that the indices for lists (sequencesstart counting with the slice operationmy_list[ ]returns list of items starting with the item indexed by up to but not including the item indexed by sometimesyou will want to initialize list this can quickly be accomplished by using repetition for examplemy_list [ my_list [ one very important aside relating to the repetition operator is that the result is repetition of references to the data objects in the sequence this can best be seen by considering the review of basic python