How to update ArcGIS online metadata using the API?

Question

I am trying to update metadata (XML file) for ArcGIS online items using the REST API but I am not quite sure how to do that.

It says in the documentation that I should be able to change the metadata on the Add Item and Update Item operations, but not exactly how:

http://resources.arcgis.com/en/help/arcgis-rest-api/index.html#//02r30000009v000000

Here is my try which returns a success but doesn't actually change the metadata.

def update_metadata(user, item, token, metadata):

    d = {'metadata': (metadata, open(metadata, 'rb')),
         "token" :token,
         "f":"json"}

    url = 'http://www.arcgis.com/sharing/rest/content/users/{0}/items/{1}/update'.format(user, item)
    r = requests.post(url, data = d)

    response = json.loads(r.content)

    if 'error' in response.keys():
        raise Exception(response['message'], response['details'])

    return response

Did anyone already successfully updated metadata for ArcGIS online items using the REST API, and if yes how?

Answer 1

Typically what I do when mimicking something from ArcGIS Online is do the same thing in ArcGIS Online while looking at the network traffic through Google Developer Tools/Fiddler. In the case of metadata, the following is the request made when saved:

I'm not entirely how this can be replicated through Python but it might give you a better idea of what is required.

Answer 2

Figured it out in the end. In the request form, I have to keep file and other payload data separate. The function below worked for me:

def update_metadata(user, item, token, metadata):

    d = {"overwrite": "true",
         "token": token,
         "f": "json"}
    f = {'metadata': ('metadata.xml', open(metadata, 'rb'), 'text/xml', {'Expires': '0'})} 

    url = 'http://www.arcgis.com/sharing/rest/content/users/{0}/items/{1}/update'.format(user, item)
    r = requests.post(url, data = d, files = f)

    response = json.loads(r.content)

    if 'error' in response.keys():
        raise Exception(response['message'], response['details'])

    return response