Page 289 - Computer Science Class 11 Without Functions
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The strings 'red', 'green', 'blue', 'pink', 'orange', 'white', and 'black' are stored at index
            0, 1, 2, 3, 4, 5, and 6 respectively. The indexes 0, 1, 2, 3, 4, 5, 6, correspond to the negative indexes -7, -6,
            -5, -4, -3, -2, and -1, respectively. To access an element in a list, the list object is followed by an opening square bracket,
            the index to be accessed, and a closing square bracket. For example,
             >>> colors[3]
                 'pink'
             >>> colors[-2]
                 'white'
            Unlike strings, lists are mutable. So, we can replace an item in a list with another item. For example,
            An empty list can be defined using square brackets [ ] or by using the list() constructor with no arguments. Here
            are both methods:

            Method 1: Using square brackets []
                emptyList = []
            Method 2: Using the list() constructor with no arguments:

                emptyList = list()
            12.1.1 List Derived from a String

            Given a string as an argument, the list() function returns a list. For example,
             >>> vowels = 'aeiou'
             >>> list(vowels)
                 ['a', 'e', 'i', 'o', 'u']
            12.1.2 Length of a List: len()

            We have already used the len() function to find the length of a string. We can also apply the len() function to find
            the number of elements in a list. For example,

             >>> len(colors)
                 7
            12.1.3 Slicing

            In the last chapter, we used slicing for accessing a subsequence of elements in a string. In this chapter, we will use
            slicing to access the subsequences of lists and tuples. Recall the following syntax for specifying a slice:
                 <start>:<finish> [:<step>]
            Note that the step is optional. Below we give some examples of slicing,
             >>> colors[3:6]
                 ['yellow', 'orange', 'white']
            The slice [3:6] yields a list comprising the elements colors[3], colors[4], and colors[5], but not
            colors[6].
            The slice  [:3]  yields the list comprising the list elements up to index 3 (excluding the element at index 3, For
            example,
             >>> colors][:3]
                 ['red', 'green', 'blue']
            Note that colors[-1] and colors[6] refer to the same position in list colors. So, the slice [1, -1] yields the
            list comprising the list elements colors[1], colors[2], …, colors[5] excluding colors[6].
             >>> colors][1:–1]
                 ['green', 'blue', 'yellow', 'orange', 'white']
            The slice  [::2] yields a list,  comprising the alternate elements of the list, because the step size is 2:
             >>> colors[::2]
                 ['red', 'blue', 'orange', 'black']



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