Append not working

[WiPi]

Hi guys,

I have used this several times before and I simply cannot see what I am doing wrong here.
Previous code has extracted a list of data (data_id) under 'tag' - I just want to retrieve it and put it in an array.
Here's my code and output.

id = []
 for id in tag:
                data_id = id.get('data-id')
                print(id.append(data_id),str(data_id))
                #load id array list
                id.append(data_id)

Output:
None 81568
None 176573
None 123466
None 124106
None 125505
None 161249
None 31776

The data is correct, just not being added to array (or rather being added as None)