Fetch an asset object

Return an asset object

Notes on Caching

Asset objects are cached by default for 2 hours (7200 seconds). Depending on the update interval of an asset object (e.g. for frequently updated data) the Cache-Control header can be different, in special cases it can even be set to no-cache (e.g. for realtime data).

All endpoints support the precondition headers If-Match and If-None-Match. To reduce unnecessary traffic it's highly recommended to use these headers (mostly If-None-Match) when making calls.

In case your application is using frequently updated data and you want to be sure not to miss an update of the data, the recommended procedure is as follows:

import requests
import time

refresh_interval = 60

item_etag = "*"
item_url = "https://data.geo.admin.ch/collections/{collectionID}/items/{itemId}"

asset_id = 'data.json'
asset_etag = "*"

poll_for_new_data = True

while(poll_for_new_data):
  item_response = requests.get(item_url, headers={'If-None-Match': f'"{item_etag}"'})
  if item_response.status_code == 304:
    # item metadata and hence any associated asset object didn't
    # change since last call

    time.sleep(refresh_interval)

  elif item_response.status_code == 200:
    # item metadata has changed since last visit

    item_etag = item_response.headers.get("ETag") # save the new etag
    asset_href = item_response.json['assets'][asset_id]['href'] # save the asset href

    obj_response = requests.get(asset_href, headers={'If-None-Match': f'"{asset_etag}"'})
    if obj_response.status_code == 304:
      # "our" asset object didn't change since last call,
      # we can ignore that the item metadata changed,
      # it was a different asset that has changed

      time.sleep(refresh_interval)

    elif obj_response.status_code == 200:
      # "our" asset object has changed, we load the new data

      asset_etag = obj_response.headers.get("ETag")  # save the new asset etag
      asset_checksum = obj_response.headers.get("X-Amz-Meta-Sha256")
      object = obj_response.data

      # calculate the sha256 checksum of the data in a proper way
      checksum = calc_checksum(object)
      if checksum != asset_checksum:
        # Error: corrupted data from download
        # do proper error handling

      # do sth with the data
    else:
      # do proper error handling
  else:
    # do proper error handling