Out Of Core CSV Transposing. Constant memory use. Arbitrary CSV size.

transpose_csv_ooc.py

    import csv
    
    def transpose_csv_out_of_core(csv_path, output_csv_path='transposed.csv', delimiter=','):
        """
        On my laptop it can transpose at ~375,000 lines a sec
        
        :param csv_path: 
        :param output_csv_path: 
        :param delimiter: 
        :return: 
        """
        transposed_iterator = zip(*csv.reader(open(csv_path)))
        with open(output_csv_path, 'w') as out:
            for row in transposed_iterator:
                out.write(delimiter.join(row) + '\n')