Copy features from one layer to another with ogr and python

Question

I have two layers with the same feature definitions named lyr and lyr_add. These layers were populated from a JSON based mapserver. I would like to append all of the features from lyr_add to lyr, but, when I use lyr.CreateFeature(feature) for a single feature, it is not appended. I would like to append the features to the lyr prior to writing it to a file. Running my python script does not result in any errors or exceptions. What should I modify in my code to successfully append the features?

An abbreviated version of my code that I have attempted is:

import ogr
import os
import sys
import urllib, json

os.chdir(r'C:\Users\pipi\Documents\Rogaine')

xmin = 16501408.594
ymin = -4372525.989
xmax = 16520000
ymax = -4320000
extent = str(xmin) + ',' + str(ymin) + ',' + str(xmax) + ','+ str(ymax)

dict = {}
dict['Creek_Unnamed']=49

def count(url):
    """Returns a count of all of the features within the provided boundary"""
    url_count = '&where=1%3D1&returnCountOnly=true'
    url = url + url_count

    response = urllib.urlopen(url)
    data = json.loads(response.read())
    count = data[u'count']
    return count

def object_list(url):
    """Returns a list of the OBJECTID'S for all of the features within the provided boundary"""
    url_id = '&returnIdsOnly=true'
    url = url + url_id
    response = urllib.urlopen(url)
    data = json.loads(response.read())
    list = data['objectIds']
    return list

url_server = "http://maps.six.nsw.gov.au/arcgis/rest/services/sixmaps/LPIMap/MapServer/"
url_2 = "/query?geometry="
url_3 = "&geometryType=esriGeometryEnvelope"
url_4 = "&f=pjson"

for key in dict:
    url = url_server + str(dict[key]) + url_2 + extent + url_3 + url_4
    count = count(url)
    if count == 0:
        pass
    else:
        ds = ogr.Open(url)
        lyr = ds.GetLayer()
        if count > 1000:
            object_list = object_list(url)
            low_bound = object_list[x*1000]
            if ((x+1)*1000) > count:
                up_bound = object_list[-1]
            else:
                up_bound = object_list[((x+1)*1000-1)]

            url_loop = "&where=OBJECTID+>%3D+" + str(low_bound) + "+AND+OBJECTID+<%3D+" +str(up_bound)
            url_2 = url + url_loop
            ds_add = ogr.Open(url_2)
            lyr_add = ds_add.GetLayer()
            for i in range(0, lyr_add.GetFeatureCount()):
                feature = lyr_add.GetFeature(i)
                lyr.CreateFeature(feature)
            del ds_add

        del ds, lyr    

Answer 1

You need to have "write" access to the data source. In this case the data source is a web page resulting from a query. One solution is to create a copy of the data source in the computer's memory, and, then add to that memory:

        #create an output datasource in memory
        mem_driver=ogr.GetDriverByName('MEMORY')
        source = mem_driver.CreateDataSource('memData')
        mem = source.CopyLayer(lyr, key)
        lyr=source.GetLayer()