An agate aggregation to generate geojson linestrings from sequential row data

linestring.py

import agate
import geojson

class LineString(agate.Aggregation):
    def __init__(self, lat_column, lng_column):
        self._lat_column_name = lat_column
        self._lng_column_name = lng_column

    def get_aggregate_data_type(self, table):
        return agate.Text()

    def validate(self, table):
        lat_column = table.columns[self._lat_column_name]
        lng_column = table.columns[self._lng_column_name]

        if not isinstance(lat_column.data_type, agate.Number) or not isinstance(lng_column.data_type, agate.Number):
            raise DataTypeError('LineString can only be applied to columns containing Number data.')

    def run(self, table):
        lat_column = table.columns[self._lat_column_name]
        lng_column = table.columns[self._lng_column_name]

        points = []

        for lat, lng in zip(lat_column, lng_column):
            points.append((float(lng), float(lat)))

        return str(geojson.LineString(points))