def pretty_format(self, show_percents=False, values_in_chart=True,
           truncate=None, sort_by_count=False):
        """
        :return: A multi-line string representation of this confusion matrix.
        :type truncate: int
        :param truncate: If specified, then only show the specified
            number of values.  Any sorting (e.g., sort_by_count)
            will be performed before truncation.
        :param sort_by_count: If true, then sort by the count of each
            label in the reference data.  I.e., labels that occur more
            frequently in the reference label will be towards the left
            edge of the matrix, and labels that occur less frequently
            will be towards the right edge.

        @todo: add marginals?
        """
        confusion = self._confusion

        values = self._values
        if sort_by_count:
            values = sorted(values, key=lambda v:
                            -sum(self._confusion[self._indices[v]]))

        if truncate:
            values = values[:truncate]

        if values_in_chart:
            value_strings = ["%s" % val for val in values]
        else:
            value_strings = [str(n+1) for n in range(len(values))]

        # Construct a format string for row values
        valuelen = max(len(val) for val in value_strings)
        value_format = '%' + repr(valuelen) + 's | '
        # Construct a format string for matrix entries
        if show_percents:
            entrylen = 6
            entry_format = '%5.1f%%'
            zerostr = '     .'
        else:
            entrylen = len(repr(self._max_conf))
            entry_format = '%' + repr(entrylen) + 'd'
            zerostr = ' '*(entrylen-1) + '.'

        # Write the column values.
        s = ''
        for i in range(valuelen):
            s += (' '*valuelen)+' |'
            for val in value_strings:
                if i >= valuelen-len(val):
                    s += val[i-valuelen+len(val)].rjust(entrylen+1)
                else:
                    s += ' '*(entrylen+1)
            s += ' |\n'

        # Write a dividing line
        s += '%s-+-%s+\n' % ('-'*valuelen, '-'*((entrylen+1)*len(values)))

        # Write the entries.
        for val, li in zip(value_strings, values):
            i = self._indices[li]
            s += value_format % val
            for lj in values:
                j = self._indices[lj]
                if confusion[i][j] == 0:
                    s += zerostr
                elif show_percents:
                    s += entry_format % (100.0*confusion[i][j]/self._total)
                else:
                    s += entry_format % confusion[i][j]
                if i == j:
                    prevspace = s.rfind(' ')
                    s = s[:prevspace] + '<' + s[prevspace+1:] + '>'
                else: s += ' '
            s += '|\n'

        # Write a dividing line
        s += '%s-+-%s+\n' % ('-'*valuelen, '-'*((entrylen+1)*len(values)))

        # Write a key
        s += '(row = reference; col = test)\n'
        if not values_in_chart:
            s += 'Value key:\n'
            for i, value in enumerate(values):
                s += '%6d: %s\n' % (i+1, value)

        return s
dataset/ETHPy150Open nltk/nltk/nltk/metrics/confusionmatrix.py/ConfusionMatrix.pretty_format/original