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To start visualization, we click the <Next> button. On executing the 1st line of code, Python creates the list lst1
        comprising values 30, 60, 10, 20, and 50 (Fig 4.12). The execution environment of the Python script is called a global
        frame. So, the visualisation shows the list lst1 in the global frame. The left panel of the code box shows two arrows
        colored in red and green respectively. While the green arrow refers to the line just executed, the red arrow points to
        the next line to be executed.
























                              Fig 4.12: Code Visualization through Python Tutor (after execution of line 1)

        As the red arrow points to line 2, clicking <Next> executes line 2. Now each of the two names (variables) lst1 and
        lst2 refers to the same list (Fig 4.13). Note that the global frame now contains two entries, one for name lst1 and
        another for lst2.

























                              Fig 4.13: Code Visualization through Python Tutor (after execution of line 2)
        Clicking  <Next>  executes  line  3  of  the  code,  and  Python  displays  the  list  lst1 and  id(lst1)in  the Print
        output box. Again, clicking <Next> executes line 4 of the code, and Python displays the list lst2 and id(lst2) in
        the Print output box. Note that id(lst1) equals id(lst2), again confirming that the names lst1 and lst2 refer
        to the same list (Fig 4.14).













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