Class structure to parse Altair Charts and store data and metadata.

ChartParser.py

from ._data import (_locate_channel_data, _locate_channel_axis, _locate_channel_field, _locate_channel_scale, 
                    _locate_channel_dtype, _convert_to_mpl_date)

class Channel(object):
    """
    Stores relevant encoding channel information.
    
    Attributes
    ----------
    channel : str
    data : np.array
    axis : dict
    bin
    field : str
    scale : dict
    sort
    stack
    timeUnit
    title
    type : str
    """
    def __init__(self, channel_name, alt_chart, df):
        self.channel = channel_name  # Not stored in the channel's information in Altair, but useful to have
        self.data = _locate_channel_data(alt_chart, channel_name)  # Not stored in the channel's information in Altair, but useful to have
        self.axis = _locate_channel_axis(alt_chart, channel_name)
        self.bin = None
        self.field = _locate_channel_field(alt_chart, channel_name)
        self.scale = _locate_channel_scale(alt_chart, channel_name)
        self.sort = None
        self.stack = None
        self.timeUnit = None
        self.title = None
        self.type = _locate_channel_dtype(alt_chart, channel_name)
        
        if self.type == 'temporal':
            self.data = _convert_to_mpl_date(self.data)


class Chart(object):
    """
    Stores Altair chart information usefully. Use this class for initially converting the Altair chart.
    
    Attributes
    ----------
    data : pd.DataFrame
    mark : str
    encoding : dict of Channels
    """
    def __init__(self,  alt_chart):
        _normalize_data(alt_chart)
        self.data = alt_chart.data
        self.mark = alt_chart.mark 
        self.encoding = {}
        for k, v in alt_chart.to_dict()['encoding'].items():
            self.encoding[k] = Channel(k, alt_chart, self.data)  # Create a Channel for each present encoding channel.
            
        ALTAIR_ENCODINGS = ['color', 'detail', 'fill', 'href', 'key', 'latitude', 'latitude2', 'longitude', 'longitude2',
                            'opacity', 'order', 'shape', 'size', 'stroke', 'text', 'tooltip', 'x', 'x2', 'y', 'y2']
       
        for i in ALTAIR_ENCODINGS:
            if i not in alt_chart.to_dict()['encoding'].keys():
                self.encoding[i] = None  # So we can have a consistent way to deal with channels that are possible in 
                                         # Altair charts in general, but not used in this one.