Python container data type-collections

#  ! /Usr/bin/Python  #  Coding = UTF-8  #  Http://docs.python.org/library/collections.html  #  Count object only 2.7  From Collections Import  Counter  #  Count the number of occurrences of letters Counter ( '  Hello World '  ) Counter ([  '  Red  ' , '  Blue  ' , '  Red  ' , '  Green  ' , '  Blue  ' ,'  Blue  '  ])  #  A value smaller than or equal to 0 is ignored. C = counter (A = 4, B = 2, c = 0, D =-2 ) List (C. Elements ())  #  Take the first three letters Counter ( '  Hello World  ' ). Most_common (3 )  #  Heap  From Collections Import  Dequed = Deque ( '  ABC  '  ) D. append (  '  D  '  ) D. Pop ()  #  Post-in-first-out D. popleft () #  First in first out  #  Returns the last n lines of text. Deque (open (filename), n)  #  Defaultdict  From Collections Import  Defaultdict  #  Use List to initialize a dict D = Defaultdict (list) d [  "  Yellow  " ]. Append (1 ) D [  "  Red  " ]. Append (2 ) D [  "  Yellow  " ]. Append (3 )  Print D. Items () #  [('Red', [2]), ('yellow', [1, 3])]  #  Use int to initiate a dict D = Defaultdict (INT) d [  "  Yellow  " ] + = 1 D [ "  Red  " ] + = 2 D [  "  Yellow  " ] + = 3 Print D. Items () #  [('Red', 2), ('yellow', 4)]