extract.py

"""Extract data on near-Earth objects and close approaches from CSV and
JSON files.

The `load_neos` function extracts NEO data from a CSV file, formatted as
described in the project instructions, into a collection of `NearEarthObject`s.

The `load_approaches` function extracts close approach data from a JSON file,
formatted as described in the project instructions, into a collection of
`CloseApproach` objects.

The main module calls these functions with the arguments provided at the
command line, and uses the resulting collections to build an `NEODatabase`.

You'll edit this file in Task 2.
"""
import csv
import json

from models import NearEarthObject, CloseApproach


def load_neos(neo_csv_path):
    """Read near-Earth object information from a CSV file.

    :param neo_csv_path: A path to a CSV file containing data about near-Earth
    objects.
    :return: A collection of `NearEarthObject`s.
    """
    neos = []
    with open(neo_csv_path, 'r') as infile:
        reader = csv.DictReader(infile)
        for elem in reader:
            neo = NearEarthObject(
                designation=elem["pdes"],
                name=elem["name"],
                hazardous=elem["pha"],
                diameter=elem["diameter"],
            )
            neos.append(neo)
    return neos


def load_approaches(cad_json_path):
    """Read close approach data from a JSON file.

    :param cad_json_path: A path to a JSON file containing data about close
    approaches.
    :return: A collection of `CloseApproach`es.
    """
    approaches = []
    with open(cad_json_path, 'r') as infile:
        contents = json.load(infile)
        for elem in contents['data']:
            approach = CloseApproach(
                neo=elem[0],
                time=elem[3],
                distance=float(elem[4]),
                velocity=float(elem[7]),
            )
            approaches.append(approach)
    return approaches