python - 如何有效地将数据从 geopandas 保存到 django(从 shapely 转换为 geodjango)？

Question

我正在使用 geopandas 操作 GIS 数据并将其存储在各种 Django 模型中。 geopandas 在底层使用了 shapely 而 Django 则没有。

这是一些代码:

import geopandas as gpd
from django.contrib.gis.db import models

class MyModel(models.Model):
  geometry = models.PolygonField()
  name = models.CharField(max_length=255, null=False, unique=True)
  some_property = models.IntegerField()

gdf = gpd.read_file("some_data.geojson")
# ...do some stuff w/ gdf...

for data in gdf.to_dict("records"):
  name = data.pop("name")
  MyModel.objects.create_or_update(
    name=name,
    defaults=data,
  )

上面的代码会失败并出现如下错误:

TypeError: Cannot set MyModel SpatialProxy (POLYGON) with value of type: <class 'shapely.geometry.polygon.Polygon'>

除非我添加一些恶心的代码，例如:

from django.contrib.gis.geos import fromstr, Polygon 
data["geometry"] = Polygon(fromstr(str(data["geometry"])))

有什么方法可以避免这种情况并直接从 shapely 映射到 Django 吗？

---

编辑:

以下是一些值:

>> data["geometry"]
<shapely.geometry.polygon.Polygon object at 0x7fb374f41908>
>> str(data["geometry"])
'POLYGON ((-4.337076919429241 53.41842814531255, -4.336698521348041 53.4182242737367, ....))'
>> fromstr(str(data["geometry"]))
<Polygon object at 0x7fb3733d158e>

Answer 1

您的解决方案并没有您想象的那么棘手。

由于您的 data['geometry'] 字段返回一个 WKT 字符串表示形式 ('POLYGON ((-4.337076919429241 53.41842814531255, ... ))) 你可以避免fromstr这一步，直接传递to a GEOSGeometry :

from django.contrib.gis.geos import GEOSGeometry

polygon = GEOSGeometry('POLYGON ((-4.337076919429241 53.41842814531255, ... ))')

您还可以添加一些错误处理，不再担心您的解决方案会崩溃 :) :

for data in gdf.to_dict("records"):
    name = data.pop("name")
    geometry_str = data.pop('geometry')        
    try:
        geometry = GEOSGeometry(geometry_str)
    except (TypeError, ValueError) as exc:
        # If the geometry_str is not a valid WKT, EWKT or HEXEWKB string
        # or is None then either continue, break or do something else.
        # I will go with continue here.
        continue

    if geometry.geom_type != 'Polygon':
        # If the created geometry is not a Polygon don't pass it on MyModel
        continue 

    MyModel.objects.update_or_create(
        name=name, geometry=geometry,
        defaults=data,
    )