Adding metadata to Azure blob with Python SDK & Azure Functions

Question

I have encountered a problem when setting blob metadata in Azure Storage. I have developed a script for this in Spyder, so local Python, which works great. Now, I want to be able to execute this same script as an Azure Function. However, when setting the metadata I get the following error: HttpResponseError: The specifed resource name contains invalid characters.

The only change from Spyder to Functions that I made is:

Spyder:

def main(container_name,blob_name,metadata):
    from azure.storage.blob import BlobServiceClient
    
    # Connection string to storage account
    storageconnectionstring=secretstoragestringnotforstackoverflow
    
    # initialize clients
    blobclient_from_connectionstring=BlobServiceClient.from_connection_string(storageconnectionstring)
    containerclient=blobclient_from_connectionstring.get_container_client(container_name)
    blob_client = containerclient.get_blob_client(blob_name)
    
    # set metadata of container
    blob_client.set_blob_metadata(metadata=metadata)

    return

Functions

def main(req: func.HttpRequest):

    container_name = req.params.get('container_name')
    blob_name = req.params.get('blob_name')
    metadata_raw = req.params.get('metadata')

    metadata_json = json.loads(metadata_raw) 
    
    # Connection string to storage account
    storageconnectionstring=secretstoragestringnotforstackoverflow
    
    # initialize clients
    blobclient_from_connectionstring=BlobServiceClient.from_connection_string(storageconnectionstring)
    containerclient=blobclient_from_connectionstring.get_container_client(container_name)
    blob_client = containerclient.get_blob_client(blob_name)
   
    # set metadata of container
    blob_client.set_blob_metadata(metadata=metadata_json)
    
    return func.HttpResponse()

Arguments to the Function are passed in the header. Problem lies with metadata and not container_name or blob_name as I get no error when I comment out metadata. Also, I tried formatting metadata in many variations with single or double quotes and as JSON or as string but no luck so far. Anyone who could help me solve this problem?

Answer 1

I was able to fix the problem. Script was fine, problem was in the input parameters. They needed to be in a specific format. metadata as a dict with double quotes and blob/container as string without any quote.

As request the function.json:

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "authLevel": "anonymous",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "$return"
    }
  ]
}

With parameter formatting: Picture from Azure Functions