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Count duplicates and show unique values in csv files: code:
        
Input:
        
Output:
        
Note that different from the next code, with the code above, only the first and the last five lines are shown if the list is too longer than 10 lines, for instance:
        

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Count duplicates and show unique values in a csv file, and then save the full list into a csv file: code:
        
With the same input as the one above, but the output is the full list saved in a csv file: