<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def run(self):
 """Reads data from disk and generates CSV files."""

        # Try to create the directory
        if not os.path.exists(self.output):
            try:
                os.mkdir(self.output)
            except:
                print 'failed to create output directory %s' % self.output

        # Be sure it is a directory
        if not os.path.isdir(self.output):
            print 'invalid output directory %s' % self.output
            sys.exit(1)

        # Create the CSV handlers
        visitors = [
            _CompaniesCSV(self.output),
            _ActivitiesCSV(self.output),
            _ActivitiesSeenCSV(self.output),
            _QSACSV(self.output),
        ]

        # Run by each company populating the CSV files
        for path in glob.glob(os.path.join(self.input, '*.json')):
            with open(path, 'r') as f:
                try:
                    data = json.load(f, encoding='utf-8')
                except ValueError:
                    continue

                for visitor in visitors:
                    visitor.visit(data)