key = issue.get('key', None)
if key:
    temp['key'] = key
fields = issue.get('fields', None)
if fields:
    customfield = fields.get('customfield_12830', None)
temp['customfield'] = customfield
progress = fields.get('progress', None)
if progress:
    total = progress.get('total', None)
temp['total'] = total
x.append(temp)
print(x)
Selecting values from a JSON file in Python