def numberify_file(self, filename):
        '''Prepend each line of a file with the line number
        Argument:
        filename - name of the file to be numberified
        '''
        try:
            fd = open(filename, 'r+')
            lines = fd.readlines()
            for i in range(len(lines)):
                if lines[i][0:len(str(i+1))] != str(i+1):
                    lines[i] = str(i+1) + ' ' + lines[i]
                else:
                    print "File already numbered"
                    return False
            fd.seek(0)
            fd.writelines(lines)
            fd.close()
            return True
        except IOError as e:
            print 'I/O error({0}): {1}'.format(e.errno, e.strerror)
        except:
            print 'Unexpected error:', exc_info()[0]
            raise