Puis-je avoir deux fonctions init dans une classe python?

Question

Je porte un code Java de géolocalisation de http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates#Java (illustré ci-dessous) à python. Il peut être initialisé en utilisant deux fonctions (fromDegrees ou fromRadians). Je pensais que je pouvais faire quelque chose comme

class geoLocation: 

    _radLat = 0 
    _radLong = 0 
    _degLat = 0 
    _degLong = 0 


    def fromDegrees(lat, long): 
     #set _radLat, _radLong, _degLat, _degLong 

    def fromRadians(lat, long): 
     #set _radLat, _radLong, _degLat, _degLong 

    ... 

Mais cela ne semble pas optimale puisque je mets les valeurs _radLat, _radLong, _degLat et _degLong deux fois. Puis-je définir deux fonctions init? Quelle est la meilleure façon de faire cela?

Merci

/** 
* <p>Represents a point on the surface of a sphere. (The Earth is almost 
* spherical.)</p> 
* 
* <p>To create an instance, call one of the static methods fromDegrees() or 
* fromRadians().</p> 
* 
* <p>This code was originally published at 
* <a href="http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates#Java"> 
* http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates#Java</a>.</p> 
* 
* @author Jan Philip Matuschek 
* @version 27 May 2010 
*/ 
public class GeoLocation { 

    private double radLat; // latitude in radians 
    private double radLon; // longitude in radians 

    private double degLat; // latitude in degrees 
    private double degLon; // longitude in degrees 

    private static final double MIN_LAT = Math.toRadians(-90d); // -PI/2 
    private static final double MAX_LAT = Math.toRadians(90d); // PI/2 
    private static final double MIN_LON = Math.toRadians(-180d); // -PI*2 
    private static final double MAX_LON = Math.toRadians(180d); // PI*2 

    private GeoLocation() { 
    } 

    /** 
    * @param latitude the latitude, in degrees. 
    * @param longitude the longitude, in degrees. 
    */ 
    public static GeoLocation fromDegrees(double latitude, double longitude) { 
     GeoLocation result = new GeoLocation(); 
     result.radLat = Math.toRadians(latitude); 
     result.radLon = Math.toRadians(longitude); 
     result.degLat = latitude; 
     result.degLon = longitude; 
     result.checkBounds(); 
     return result; 
    } 

    /** 
    * @param latitude the latitude, in radians. 
    * @param longitude the longitude, in radians. 
    */ 
    public static GeoLocation fromRadians(double latitude, double longitude) { 
     GeoLocation result = new GeoLocation(); 
     result.radLat = latitude; 
     result.radLon = longitude; 
     result.degLat = Math.toDegrees(latitude); 
     result.degLon = Math.toDegrees(longitude); 
     result.checkBounds(); 
     return result; 
    } 

    private void checkBounds() { 
     if (radLat < MIN_LAT || radLat > MAX_LAT || 
       radLon < MIN_LON || radLon > MAX_LON) 
      throw new IllegalArgumentException(); 
    } 

    /** 
    * @return the latitude, in degrees. 
    */ 
    public double getLatitudeInDegrees() { 
     return degLat; 
    } 

    /** 
    * @return the longitude, in degrees. 
    */ 
    public double getLongitudeInDegrees() { 
     return degLon; 
    } 

    /** 
    * @return the latitude, in radians. 
    */ 
    public double getLatitudeInRadians() { 
     return radLat; 
    } 

    /** 
    * @return the longitude, in radians. 
    */ 
    public double getLongitudeInRadians() { 
     return radLon; 
    } 

    @Override 
    public String toString() { 
     return "(" + degLat + "\u00B0, " + degLon + "\u00B0) = (" + 
       radLat + " rad, " + radLon + " rad)"; 
    } 

    /** 
    * Computes the great circle distance between this GeoLocation instance 
    * and the location argument. 
    * @param radius the radius of the sphere, e.g. the average radius for a 
    * spherical approximation of the figure of the Earth is approximately 
    * 6371.01 kilometers. 
    * @return the distance, measured in the same unit as the radius 
    * argument. 
    */ 
    public double distanceTo(GeoLocation location, double radius) { 
     return Math.acos(Math.sin(radLat) * Math.sin(location.radLat) + 
       Math.cos(radLat) * Math.cos(location.radLat) * 
       Math.cos(radLon - location.radLon)) * radius; 
    } 

    /** 
    * <p>Computes the bounding coordinates of all points on the surface 
    * of a sphere that have a great circle distance to the point represented 
    * by this GeoLocation instance that is less or equal to the distance 
    * argument.</p> 
    * <p>For more information about the formulae used in this method visit 
    * <a href="http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates"> 
    * http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates</a>.</p> 
    * @param distance the distance from the point represented by this 
    * GeoLocation instance. Must me measured in the same unit as the radius 
    * argument. 
    * @param radius the radius of the sphere, e.g. the average radius for a 
    * spherical approximation of the figure of the Earth is approximately 
    * 6371.01 kilometers. 
    * @return an array of two GeoLocation objects such that:<ul> 
    * <li>The latitude of any point within the specified distance is greater 
    * or equal to the latitude of the first array element and smaller or 
    * equal to the latitude of the second array element.</li> 
    * <li>If the longitude of the first array element is smaller or equal to 
    * the longitude of the second element, then 
    * the longitude of any point within the specified distance is greater 
    * or equal to the longitude of the first array element and smaller or 
    * equal to the longitude of the second array element.</li> 
    * <li>If the longitude of the first array element is greater than the 
    * longitude of the second element (this is the case if the 180th 
    * meridian is within the distance), then 
    * the longitude of any point within the specified distance is greater 
    * or equal to the longitude of the first array element 
    * <strong>or</strong> smaller or equal to the longitude of the second 
    * array element.</li> 
    * </ul> 
    */ 
    public GeoLocation[] boundingCoordinates(double distance, double radius) { 

     if (radius < 0d || distance < 0d) 
      throw new IllegalArgumentException(); 

     // angular distance in radians on a great circle 
     double radDist = distance/radius; 

     double minLat = radLat - radDist; 
     double maxLat = radLat + radDist; 

     double minLon, maxLon; 
     if (minLat > MIN_LAT && maxLat < MAX_LAT) { 
      double deltaLon = Math.asin(Math.sin(radDist)/
       Math.cos(radLat)); 
      minLon = radLon - deltaLon; 
      if (minLon < MIN_LON) minLon += 2d * Math.PI; 
      maxLon = radLon + deltaLon; 
      if (maxLon > MAX_LON) maxLon -= 2d * Math.PI; 
     } else { 
      // a pole is within the distance 
      minLat = Math.max(minLat, MIN_LAT); 
      maxLat = Math.min(maxLat, MAX_LAT); 
      minLon = MIN_LON; 
      maxLon = MAX_LON; 
     } 

     return new GeoLocation[]{fromRadians(minLat, minLon), 
       fromRadians(maxLat, maxLon)}; 
    } 

} 

Answer 1

par défaut (Choisissez l'une radians ou degrés) et de s'y tenir. Vous pouvez écrire un classmethod pour convertir automatiquement en l'autre:

class geoLocation: 
    def __init__(self, lat, long): 
     """init class from lat,long as radians""" 

    @classmethod 
    def fromDegrees(cls, dlat, dlong): 
     """creat `cls` from lat,long in degrees """ 
     return cls(to_radians(dlat), to_radians(dlong)) 

    @classmethod 
    def fromRadians(cls, lat, long): # just in case 
     return cls(lat, long) 

obj = geoLocation.fromDegrees(10,20) # returns a new geoLocation object 

Answer 2

Je voudrais simplement inclure un booléen dans votre méthode d'initialisation. Au lieu d'avoir deux méthodes __init__, procédez comme suit:

class geoLocation: 
    def __init__(self, lat, long, degrees=True): 
     if degrees: 
      # process as fromDegrees 
      (self._radLat, self._radLong, self._degLat, self._degLong) = self.fromDegrees(lat, long) 
     else: 
      (self._radLat, self._radLong, self._degLat, self._degLong) = self.fromRadians(lat, long) 

    def fromDegrees(self, lat, long): 
     # some function returning radLat and long and degLat and long in a tuple 
    def fromRadians(self, lat, long): 
     # same idea but different calculations 

Answer 3

Une autre option est d'avoir des sous-classes de GeoLocation, dire DegreesGeoLocation et RadiansGeoLocation. Vous pouvez maintenant donner à chacun sa propre fonction d'initialisation.

Vous stockez maintenant l'emplacement deux fois dans votre classe, une fois en utilisant les radians et une fois en utilisant les degrés. Cela peut causer des problèmes si vous modifiez accidentellement une représentation mais oubliez l'autre. Je pense que vous pourriez mieux utiliser une représentation, et fournir des getters et setters qui finissent par faire la conversion à l'autre représentation.

Answer 4

Une option est d'utiliser des méthodes de classe d'usine:

class geoLocation(object): 
    @classmethod 
    def fromDegrees(cls, lat, long): 
     return cls(lat, long, True) 

    @classmethod 
    def fromDegrees(cls, lat, long): 
     return cls(lat, long, False) 

    def __init__(self, lat, long, degrees=True): 
     if degrees: 
      #blah 
     else: 
      #blah