Question

我想初始化一个单点的路径。我很困惑如何去做这件事。 GeoPoint是我们创建的另一个带有name，lat和long的类。如果我创建一个新的路径，输出应该是[name（lat，long）。任何帮助都会非常感激.Init很混乱，因为我刚开始使用java中的python。

class Path :
    def __init__ (self,start_point) :
        """
        Creates a path with a single point.
        >>> Path(GeoPoint('p0',10,12))
        [p0(10,12)]
        >>> Path(GeoPoint('p3',3,1))
        [p3(3,1)]
        """

Answer 1

路径将是点/位置的有序列表。根据您的描述，您可以将Path实现为GeoPoint个对象的列表。据推测，GeoPoint类提供了有用的方法，例如，计算自身与另一个GeoPoint对象之间的距离，或者可能在地图上绘制自己。您不希望丢失该功能，因此没有理由（基于您的问题中的信息）将GeoPoint转换为其他对象只是为了将其存储在列表中。您无需访问GeoPoint对象的成员即可执行此操作。

from math import radians, cos, sin, asin, sqrt

def haversine(lon1, lat1, lon2, lat2):
    """
    Calculate the great circle distance between two points 
    on the earth (specified in decimal degrees).
    Taken from http://stackoverflow.com/a/4913653/21945
    """
    # convert decimal degrees to radians 
    lon1, lat1, lon2, lat2 = map(radians, [lon1, lat1, lon2, lat2])

    # haversine formula 
    dlon = lon2 - lon1 
    dlat = lat2 - lat1 
    a = sin(dlat/2)**2 + cos(lat1) * cos(lat2) * sin(dlon/2)**2
    c = 2 * asin(sqrt(a)) 
    r = 6371 # Radius of earth in kilometers. Use 3956 for miles
    return c * r

class GeoPoint(object):
    def __init__(self, name, latitude, longitude):
        self.name = name
        self.latitude = latitude
        self.longitude = longitude

    def __unicode__(self):
        return u'{}({},{})'.format(self.name, self.latitude, self.longitude)

    def __repr__(self):
        return self.__unicode__().encode('utf-8')

    def distance_to(self, to):
        return haversine(self.longitude, self.latitude,
                         to.longitude, to.latitude)

class Path(list):
    def __init__(self, *points):
        """ 
        Basically Path is a builtin list, but one that can be initialised with 
        multiple arguments.

        """ 
        super(Path, self).__init__(points)

样本使用：

>>> sydney = GeoPoint('Sydney', -33.8600, 151.2094)
>>> sydney
Sydney(-33.86,151.2094)
>>> hawaii = GeoPoint('Hawaii', 21.3114, -157.7964)
>>> los_angeles = GeoPoint('Los Angeles', 34.05, -118.25)
>>> new_york = GeoPoint('New York', 40.7127, -74.0059)
>>> london = GeoPoint('London', 51.5072, -0.1275)
>>> dubai = GeoPoint('Dubai', 24.9500, 55.3333)

>>> single_point = Path(sydney)
>>> single_point
[Sydney(-33.86,151.2094)]

>>> world_trip = Path(sydney, hawaii, los_angeles, new_york)
>>> print world_trip
[Sydney(-33.86,151.2094), Hawaii(21.3114,-157.7964), Los Angeles(34.05,-118.25), New York(40.7127,-74.0059)]
>>> world_trip.extend(Path(london, dubai))    # using standard list methods
>>> world_trip.append(sydney)
>>> print world_trip
[Sydney(-33.86,151.2094), Hawaii(21.3114,-157.7964), Los Angeles(34.05,-118.25), New York(40.7127,-74.0059), London(51.5072,-0.1275), Dubai(24.95,55.3333), Sydney(-33.86,151.2094)]

>>> for a, b in zip(world_trip, world_trip[1:]):
...     print '{0.name} to {1.name} : {2:.2f} km'.format(a, b, a.distance_to(b))
Sydney to Hawaii : 8165.01 km
Hawaii to Los Angeles : 4110.87 km
Los Angeles to New York : 3933.91 km
New York to London : 5566.75 km
London to Dubai : 5495.09 km
Dubai to Sydney : 12022.22 km

Answer 2

我猜你的Geopoint类有一些属性需要获取并添加到路径中的列表中。

可能路径也有某种功能可以为它添加更多点数。在init中，self.points = [start_point]就足以将第一个点添加到列表中。

某些功能可能会添加以下每一点

def add_point(self, point):
  self.points += [point]

init，创建一个带有单点的路径，python

2 个答案: