def __init__(self, a, b, ignore_fields=[], numdiffs=10, tolerance=0.0):

        self.ignore_fields = set(ignore_fields)
        self.numdiffs = numdiffs
        self.tolerance = tolerance

        self.common_columns = []
        self.common_column_names = set()

        # self.diff_columns contains columns with different column definitions,
        # but not different column data. Column data is only compared in
        # columns that have the same definitions
        self.diff_rows = ()
        self.diff_column_count = ()
        self.diff_columns = ()

        # If two columns have the same name+format, but other attributes are
        # different (such as TUNIT or such) they are listed here
        self.diff_column_attributes = []

        # Like self.diff_columns, but just contains a list of the column names
        # unique to each table, and in the order they appear in the tables
        self.diff_column_names = ()
        self.diff_values = []

        self.diff_ratio = 0
        self.diff_total = 0

        super(TableDataDiff, self).__init__(a, b)
See `FITSDiff` for explanations of the initialization parameters.
dataset/ETHPy150Open spacetelescope/PyFITS/pyfits/diff.py/TableDataDiff.__init__