collections_example

from collections import Counter 
Counter([1,1,1,2,3,2,2,])
# 返回字典统计key的个数
Counter(list).most_common()
# 常见的几个

from collections import defaultdict
nums = defaultdict(int)
nums['one'] = 1
nums['two'] = 2
print(nums['three'])
# 输出为0

from collections import OrderedDict
# 输出顺序字典