Charge sign text

def charge_sign(self):
        """Charge sign text"""
        if self.charge > 0:
            sign = "+"
        elif self.charge < 0:
            sign = "–"  # en dash, not hyphen-minus
        else:
            return ""
        ab = abs(self.charge)
        if ab > 1:
            return str(ab) + sign
        return sign