Let say that there are some yearly statistic data stored a list of Counters.
We want to find the MIN/MAX values in each month across the different years.
For example, for January it would be 10. And for February it would be 15.
We need to store the results in a new Counter.
from collections import Counter
stat2011 = Counter({"January": 12, "February": 20, "March": 50, "April": 70, "May": 15,
"June": 35, "July": 30, "August": 15, "September": 20, "October": 60,
"November": 13, "December": 50})
stat2012 = Counter({"January": 36, "February": 15, "March": 50, "April": 10, "May": 90,
"June": 25, "July": 35, "August": 15, "September": 20, "October": 30,
"November": 10, "December": 25})
stat2013 = Counter({"January": 10, "February": 60, "March": 90, "April": 10, "May": 80,
"June": 50, "July": 30, "August": 15, "September": 20, "October": 75,
"November": 60, "December": 15})
stat_list = [stat2011, stat2012, stat2013]
print reduce(lambda x, y: x & y, stat_list) # MIN
print reduce(lambda x, y: x | y, stat_list) # MAX