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12                                                   LISTS AND TUPLES














          Chapter Outline


          12.1   Lists                                       12.2  List Assignment
          12.3   Traversing a List                           12.4  Nested Lists
          12.5   Heterogeneous List                          12.6  More Operations on Lists
          12.7   Using Python's Built-in Functions with List   12. 8  List Methods
          12.9   Linear Search                               12.10  Tuples
          12.11  Tuple Operations                            12.12  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.


        12.1 Lists

        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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