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13                                                   LISTS AND TUPLES














          Chapter Outline


          13.1 List                                          13.2 Traversing a List
          13.3 Nested Lists                                  13.4 Heterogeneous List
          13.5 More Operations on Lists                      13.6 List Methods
          13.7 Tuples                                        13.8 Tuple Operations
          13.9 Tuple Methods





        Introduction
        In the last chapter, we learnt about strings and their several applications. However, a string is an immutable object,
        and we cannot modify the elements of a string. Also, the elements of a string are constrained to be characters. These
        restrictions are too harsh to develop practical applications. For example, while dealing with the students' data, we may
        like to store their roll numbers, names, addresses, academic records, etc. Also, the data relating to a student, such as
        his/her address and academic record, may change over a period of time. To deal with such situations, in this chapter
        we will discuss two types of objects, namely, lists and tuples. Elements of a list or tuple may be of arbitrary types.
        Whereas lists are mutable, tuples are immutable. Like strings, objects in a list appear in sequence and can be accessed
        using indexes.

        13.1 List

        A list comprises a comma-separated sequence of objects enclosed in square brackets []. Like strings, elements of a list
        may be accessed using indexing. Let us begin by creating a list of colours.
         >>> colors = ['red', 'green', 'blue', 'pink', 'orange', 'white', 'black']
         >>> colors
              ['red', 'green', 'blue', 'pink', 'orange', 'white', 'black']

            Non-negative      0           1           2           3            4             5          6
            indices

                             'red'     'green'      'blue'      'pink'      'orange'      'white'     'black'


            Negative          -7         -6          -5          -4            -3           -2          -1
            indices

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