Python GeoAlchemy pg_function.geojson无法使用json.loads进行解码
鉴于此功能:Python GeoAlchemy pg_function.geojson无法使用json.loads进行解码,python,sqlalchemy,flask,geoalchemy,Python,Sqlalchemy,Flask,Geoalchemy,鉴于此功能: 功能是SQLAlchemy对象的列表 template只是一个表示向用户显示内容的模板的字典 def get_feature_dictionary(features, template): feature_list = [] print features for feature in features: for field in template.fields: if field.data_type == 'geometry':
功能
是SQLAlchemy对象的列表
template
只是一个表示向用户显示内容的模板的字典
def get_feature_dictionary(features, template):
feature_list = []
print features
for feature in features:
for field in template.fields:
if field.data_type == 'geometry':
geometry = getattr(feature, field.name)
geometry_string = db.session.scalar(pg_functions.geojson(getattr(feature, field.name)))
this_feature = {
"type": "Feature",
"geometry": json.loads(geometry_string),
"properties": {
"id": feature.id,
"created": feature.created,
"status": feature.status
}
}
feature_list.append(this_feature)
return feature_list
我想返回一个GeoJSON FeatureCollection,如下所示:
{
"type": "FeatureCollection",
"features": [
{
"geometry": {
"type":"GeometryCollection",
"geometries":[
{"type":"Point","coordinates":[2,0]}
]
},
"properties": {
"created": "Tue, 03 Aug 2010 17:11:13 GMT",
"id": 1,
"status": "public"
},
"type": "Feature"
}
],
"properties": {
"features_per_page": "",
"status": {
"code": 200,
"type": "OK"
},
"total_features": 1021,
"total_pages": ""
}
}
我可以把它打印出来:
{
"type": "FeatureCollection",
"features": [
{
"geometry": '{\"type\":\"GeometryCollection\",\"geometries\":[{\"type\":\"Point\",\"coordinates\":[2,0]},{\"type\":\"Polygon\",\"coordinates\":[[[0,0],[1,0],[1,1],[0,1],[0,0]]]}]}'
],
"properties": {
"features_per_page": "",
"status": {
"code": 200,
"type": "OK"
},
"total_features": 1021,
"total_pages": ""
}
}
但我最后的错误是:
TypeError: expected string or buffer
TypeError
TypeError: expected string or buffer
Traceback (most recent call last)
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "[--removed--]/modules/api/views.py", line 116, in index
search = get_search_results(feature_type, conditions, FeatureType)
File "[--removed--]/modules/api/search.py", line 499, in get_search_results
data = get_feature_dictionary(search['results'], template)
File "[--removed--]/modules/api/utilities.py", line 241, in get_feature_dictionary
Display the sourcecode for this frameOpen an interactive python shell in this frame"geometry": json.loads(geometry_string),
File "/usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/__init__.py", line 338, in loads
return _default_decoder.decode(s)
File "/usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.py", line 365, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
TypeError: expected string or buffer
我尝试使用str()
更改类型,但这只会导致:
ValueError: No JSON object could be decoded
我已经用GeoAlchemy(pg_functions.geojson)和GeoAlchemy2(ST_AsGeoJSON)尝试了这一点,得到了相同的结果。我知道我很接近,但由于某些原因,我没有正确地传递标量或其他东西
有人知道我做错了什么吗?我发现我提出
ValueError:No-JSON对象无法解码的原因是因为我没有检查值是否存在
我改变了这一点:
geometry\u string=db.session.scalar(pg\u functions.geojson(getattr(feature,field.name)))
为此:
geometry\u string=db.session.scalar(pg\u functions.geojson(getattr(feature,field.name)))或“{}”
一切都很完美,json.loads()
被一个空字符串绊倒,无法将空字符串解析为json,它至少需要一个空json对象{}
我在这里看到了这个建议,但我仍然得到了上面的错误和回溯。。。。