从shapefile MultiPolygons创建匀称的MultiPolygons

我正在使用Fiona读取shapefile：

with fiona.open('data/boroughs/boroughs_n.shp') as source:
   mpolys = [p for p in source]
candidate = polys[0]['geometry']

这给了我一个包含坐标列表列表的字典，并键入“ MultiPolygon”。但是，我不确定如何使用坐标数据来创建Shapely MultiPolygon，因为它需要 a sequence of exterior ring and hole list tuples: [((a1, ..., aM), [(b1, ..., bN), ...]), ...].

有没有使用Fiona和Shapely的“正确”方法？

您可以使用Shapely的形状功能：

from shapely.geometry import shape
c = fiona.open('data/boroughs/boroughs_n.shp')
pol = c.next()
geom = shape(pol['geometry'])

而MultiPolygon是Polygons的列表，因此

Multi = MultiPolygon([shape(pol['geometry']) for pol in fiona.open('data/boroughs/boroughs_n.shp')]) 

我的数据之一的示例：

# the dictionaries
for pol in fiona.open('poly.shp'):
print pol['geometry']

{'type': 'Polygon', 'coordinates': [[(249744.23153029341, 142798.16434689672),   (250113.79108725351, 142132.95714436853), (250062.62130244367, 141973.76225829343), (249607.77877080048, 141757.71205576291), (249367.77424759799, 142304.68402918623), (249367.77424759799, 142304.68402918623), (249744.23153029341, 142798.16434689672)]]}
{'type': 'Polygon', 'coordinates': [[(249175.78991730965, 142292.53526406409), (249367.77424759799, 142304.68402918623), (249607.77877080048, 141757.71205576291), (249014.45396077307, 141876.13484290778), (249175.78991730965, 142292.53526406409)]]}
{'type': 'Polygon', 'coordinates': [[(249026.74622412826, 142549.13626160321), (249223.42243781092, 142496.89414234375), (249175.78991730965, 142292.53526406409), (249026.74622412826, 142549.13626160321)]]}
...

和

 # MultiPolygon from the list of Polygons
 Multi = MultiPolygon([shape(pol['geometry']) for pol in fiona.open('poly.shp')])
 Multi.wkt
'MULTIPOLYGON (((249744.2315302934148349 142798.1643468967231456, 250113.7910872535139788 142132.9571443685272243, 250062.6213024436729029 141973.7622582934272941, 249607.7787708004761953 141757.7120557629095856, 249367.7742475979903247 142304.6840291862317827, 249367.7742475979903247 142304.6840291862317827, 249744.2315302934148349 142798.1643468967231456)), ((249175.7899173096520826 142292.5352640640921891, 249367.7742475979903247 142304.6840291862317827, 249607.7787708004761953 141757.7120557629095856, 249014.4539607730694115 141876.1348429077770561, 249175.7899173096520826 142292.5352640640921891)), ((249026.7462241282628383 142549.1362616032129154, 249223.4224378109211102 142496.8941423437499907, 249175.7899173096520826 142292.5352640640921891, 249026.7462241282628383 142549.1362616032129154)), ((249244.9338986824732274 142733.5202119307068642, 249744.2315302934148349 142798.1643468967231456, 249367.7742475979903247 142304.6840291862317827, 249367.7742475979903247 142304.6840291862317827, 249367.7742475979903247 142304.6840291862317827, 249175.7899173096520826 142292.5352640640921891, 249223.4224378109211102 142496.8941423437499907, 249244.9338986824732274 142733.5202119307068642)), ((249870.8182051893090829 142570.3083320840960369, 250034.3015973484434653 142613.6706442178401630, 250152.6146321419219021 142438.5058914067049045, 250015.3392731740023009 142310.1704097116598859, 249870.8182051893090829 142570.3083320840960369)))'

另请参阅在shapefile中附加对MultiPolygons的支持

如果速度是一个问题，则从原始坐标创建多边形的速度更快。

这比以前建议的解决方案快大约5倍，之前建议的解决方案是首先创建多个多边形对象，然后根据这些对象创建多多边形对象。

这是操作方法：

# first retrieve the coordinates from your geojson dictionary
rawcoords = candidate["coordinates"]

# define the conversion function
def PrepCoordsForShapely(rawcoords):
    preppedcoords = []
    #according to the geojson specs, a multipolygon is a list of linear rings, so we loop each
    for eachpolygon in rawcoords:
        #the first linear ring is the coordinates of the polygon, and shapely needs it to be a tuple
        tupleofcoords = tuple(eachpolygon[0])
        #the remaining linear rings, if any, are the coordinates of inner holes, and shapely needs these to be nested in a list
        if len(eachpolygon) > 1:
            listofholes = list(eachpolygon[1:])
        else:
            listofholes = []
        #shapely defines each polygon in a multipolygon with the polygoon coordinates and the list of holes nested inside a tuple
        eachpreppedpolygon = (tupleofcoords, listofholes)
        #so append each prepped polygon to the final multipolygon list
        preppedcoords.append(eachpreppedpolygon)
    #finally, the prepped coordinates need to be nested inside a list in order to be used as a star-argument for the MultiPolygon constructor.
    return [preppedcoords]

# use the function to prepare coordinates for MultiPolygon
preppedcoords = PrepCoordsForShapely(rawcoords)
# use the prepped coordinates as a star-argument for the MultiPolygon constructor
shapelymultipolygon = MultiPolygon(*preppedcoords)