<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _scanDataFiles(self, dataDir, patterns):
 """ Scans the specified directory for files with the specified globbing pattern and calls self._addDataFile for each. Raises an EmptyDirException if no data files are found. """

        numDataFiles = 0
        for pattern in patterns:
            scanPath = os.path.join(dataDir, pattern)
            for filename in glob.glob(scanPath):
                self._addDataFile(filename)
                numDataFiles += 1
        if numDataFiles == 0:
            raise exceptions.EmptyDirException(dataDir, patterns)