71. class ColorBandsField: Color-band sequence

71. `class ColorBandsField`: Color-band sequence

For the format of this field, see the specification.

Unlike other classes derived from FieldItem, this class parses a variable-length field for the color-band sequence, since this field appears only in the free-form, variable-length tail section.

baseclasses.py

# - - - - -   c l a s s   C o l o r B a n d s F i e l d   - - - - -

class ColorBandsField(FieldItem):
    """Represents a color-band sequence.

      Exports: as inherited.
    """

71.1. `ColorBandsField.scanField()`

This method parses a color-band string. Although a color-band string must technically contain exactly one slash (/), one letter S, and at least one color code (with “?” allowed for unreadable characters), we don't need to check all that. We can treat the field as an arbitrary string of any number of characters in that set. The class attribute COLOR_PAT describes just that; the re.IGNORECASE flag tells the regular expression to be case-insensitive.

baseclasses.py

# - - -   C o l o r B a n d s F i e l d . s c a n F i e l d   - - -

    COLOR_PAT  =  re.compile ( r'[KWRGYBOMS?/ ]+', re.IGNORECASE )

#   @staticmethod
    def scanField ( encounter, scan, fieldName ):
        """Scan a color-bands field.
        """

        #-- 1 --
        # [ if scan starts with a pattern that matches
        #   self.COLOR_PAT ->
        #     scan    :=  scan advanced past that pattern
        #     colors  :=  that pattern, uppercased
        #   else ->
        #     Log()  +:=  error message(s)
        #     raise SyntaxError ]
        m  =  scan.tabReMatch ( ColorBandsField.COLOR_PAT )
        if  m is None:
            scan.syntax ( "Expecting a color-band group." )
        else:
            colors  =  m.group().upper()

        #-- 2 --
        # [ if len(colors) <= COLOR_BANDS_L ->
        #     self.(COLOR_BANDS_ATTR)  :=  colors, right-filled
        #         to size COLOR_BANDS_L
        #   else ->
        #     Log()  +:=  error message(s)
        #     raise SyntaxError ]
        if  len ( colors ) <= COLOR_BANDS_L:
            setattr ( encounter, COLOR_BANDS_ATTR,
                      ColorBandsField ( encounter, colors ) )
        else:
            scan.syntax ( "Color-band field '%s' too long; no more "
                          "than %d characters." %
                          (colors, COLOR_BANDS_L) )

    scanField  =  staticmethod ( scanField )

IBP banding data system: Internal maintenance specification