>>> d = requests.get("http://labels.wmflabs.org/campaigns/ruwiki/10/?tasks").json()
>>> counts = {}
>>> for t in d['tasks']:
...     counts[len(t['labels'])] = counts.get(len(t['labels']), 0) + 1
... 
>>> counts
{0: 82, 1: 4985, 2: 126}