import collections.Counter

c = Counter()                           # a new, empty counter
c = Counter('gallahad')                 # a new counter from an iterable
c = Counter({'red': 4, 'blue': 2})      # a new counter from a mapping
c = Counter(cats=4, dogs=8)             # a new counter from keyword args

import collections.Counter

c = Counter(['eggs', 'ham'])
c['bacon'] # 0
c['eggs'] # 1

c['sausage'] = 0                        # counter entry with a zero count
del c['sausage']                        # del actually removes the entry

c = Counter(a=4, b=2, c=0, d=-2)
sorted(c.elements()) #['a', 'a', 'a', 'a', 'b', 'b']

Counter('abracadabra').most_common(3)
[('a', 5), ('b', 2), ('r', 2)]

c = Counter(a=4, b=2, c=0, d=-2)
d = Counter(a=1, b=2, c=3, d=4)
c.subtract(d)
print(c) # Counter({'a': 3, 'b': 0, 'c': -3, 'd': -6})