GeoJSON响应中逆转经纬度坐标的Pythonic方法
我想把这个JSON响应中的坐标顺序从（纬度，经度）改成（经度，纬度）：
url='https://www.sciencebase.gov/catalogMaps/mapping/ows/5342c5fce4b0aa151574a8ed?\
service=wfs&version=1.1.0&request=GetFeature&typeNames=sb:Conservation_Zone_WGS84&outputFormat=application/json'
response = requests.get(url).json()
print response
{u'crs': {u'properties': {u'code': u'4326'}, u'type': u'EPSG'},
u'features': [{u'geometry': {u'coordinates': [[[[39.81487959537135,
-74.09688169446223],
[39.81488113835475, -74.09587338924456],
[39.8143317590967, -74.09614209870023],
[39.8137616151959, -74.09633047532941],
[39.812950626580545, -74.09670529470912],
[39.8120075697193, -74.09698124228382],
[39.814255381955064, -74.0973277412355],
[39.81487959537135, -74.09688169446223]]]],
u'type': u'MultiPolygon'},
u'geometry_name': u'the_geom',
u'id': u'Conservation_Zone_WGS84.1',
u'properties': {u'ID': 1,
u'NAME': u'Sedge Island Marine Conservation Zone',
u'OBJECTID': 1,
u'SHAPE_AREA': 70259289.0821,
u'SHAPE_LEN': 40592.8006466,
u'WEB_LINK': u'http://www.state.nj.us/dep/fgw/sedge.htm'},
u'type': u'Feature'}],
u'type': u'FeatureCollection'}
我可以把它拆开，强行处理，然后再组合起来，但我在想：有没有一种更优雅的Python方法来改变顺序，同时保持结构不变呢？
4 个回答
2
你的“python风格”的代码看起来很难懂，而且还不能正常运行。保持简单就好：
def swapCoords(x):
out = []
for iter in x:
if isinstance(iter, list):
out.append(swapCoords(iter))
else:
return [x[1], x[0]]
return out
for feature in response['features']:
feature['geometry']['coordinates'] = swapCoords(feature['geometry']['coordinates'])
2
好吧……要处理你的坐标列表，需要这样做：
d['features'][0]['geometry']['coordinates'][0][0]
所以要把它们反转，你需要这样做：
d['features'][0]['geometry']['coordinates'][0][0] = [i[::-1] for i in d['features'][0]['geometry']['coordinates'][0][0]]
或者，我觉得这样做会更简洁一些：
for l in d['features'][0]['geometry']['coordinates'][0][0]:
l.reverse()
2
使用列表推导式，并将结果重新赋值给结构。
这里涉及到几个列表，所以需要用到几个循环：
for feature in response['features']:
feature['geometry']['coordinates'] = [[
[[long, lat] for lat, long in coords] for coords in poly]
for poly in feature['geometry']['coordinates']]
这假设了'coordinates'的结构是稳定的；我看到还有一个'type'的键，如果使用的类型不是u'MultiPolygon'，你可能需要调整一下修改结构的方法。
这将数据从：
>>> pprint.pprint(response)
{u'crs': {u'properties': {u'code': u'4326'}, u'type': u'EPSG'},
u'features': [{u'geometry': {u'coordinates': [[[[39.81487959537135,
-74.09688169446223],
[39.81488113835475,
-74.09587338924456],
[39.8143317590967,
-74.09614209870023],
[39.8137616151959,
-74.09633047532941],
....
[39.814255381955064,
-74.0973277412355],
[39.81487959537135,
-74.09688169446223]]]],
u'type': u'MultiPolygon'},
u'geometry_name': u'the_geom',
u'id': u'Conservation_Zone_WGS84.1',
u'properties': {u'ID': 1,
u'NAME': u'Sedge Island Marine Conservation Zone',
u'OBJECTID': 1,
u'SHAPE_AREA': 70259289.0821,
u'SHAPE_LEN': 40592.8006466,
u'WEB_LINK': u'http://www.state.nj.us/dep/fgw/sedge.htm'},
u'type': u'Feature'}],
u'type': u'FeatureCollection'}
转换为：
>>> pprint.pprint(response)
{u'crs': {u'properties': {u'code': u'4326'}, u'type': u'EPSG'},
u'features': [{u'geometry': {u'coordinates': [[[[-74.09688169446223,
39.81487959537135],
[-74.09587338924456,
39.81488113835475],
[-74.09614209870023,
39.8143317590967],
[-74.09633047532941,
39.8137616151959],
....
[-74.0973277412355,
39.814255381955064],
[-74.09688169446223,
39.81487959537135]]]],
u'type': u'MultiPolygon'},
u'geometry_name': u'the_geom',
u'id': u'Conservation_Zone_WGS84.1',
u'properties': {u'ID': 1,
u'NAME': u'Sedge Island Marine Conservation Zone',
u'OBJECTID': 1,
u'SHAPE_AREA': 70259289.0821,
u'SHAPE_LEN': 40592.8006466,
u'WEB_LINK': u'http://www.state.nj.us/dep/fgw/sedge.htm'},
u'type': u'Feature'}],
u'type': u'FeatureCollection'}
4
这是一个使用 numpy 的解决方案，适用于任何 geojson 文件。它会翻转所有的“坐标”。
import json
import requests
import numpy as np
def flip_geojson_coordinates(geo):
if isinstance(geo, dict):
for k, v in geo.iteritems():
if k == "coordinates":
z = np.asarray(geo[k])
f = z.flatten()
geo[k] = np.dstack((f[1::2], f[::2])).reshape(z.shape).tolist()
else:
flip_geojson_coordinates(v)
elif isinstance(geo, list):
for k in geo:
flip_geojson_coordinates(k)
url = "https://www.sciencebase.gov/catalogMaps/mapping/ows/5342c5fce4b0aa151574a8ed?\
service=wfs&version=1.1.0&request=GetFeature&typeNames=sb:Conservation_Zone_WGS84&outputFormat=application/json"
resp = requests.get(url)
gj = json.loads(resp.text)
print gj
flip_geojson_coordinates(gj)
print gj