python dictionary sorting in descending order based on values

Question

I want to sort this dictionary d based on value of sub key key3 in descending order  See below   d      123      key1   3   key2   11   key3   3           124      key1   6   key2   56   key3   6           125      key1   7   key2   44   key3   9            So final dictionary would look like this   d      125      key1   7   key2   44   key3   9           124      key1   6   key2   56   key3   6           123      key1   3   key2   11   key3   3            My approach was to form another dictionary e from d  whose key would be value of key3 and then  use reversed sorted e   but since value of key3 can be same  so dictionary e lost some of the keys and their values  makes sense   How I can accomplish this  This is not a tested code  I am just trying to understand the logic

User · Answer

You can use dictRysan library  I think that will solve your task  import dictRysan as ry  d      123      key1   3   key2   11   key3   3           124      key1   6   key2   56   key3   6           125      key1   7   key2   44   key3   9           changed d ry nested 2L value sort d  quot key3 quot  True  print changed d

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sort dictionary  in dict  by value in decreasing order  sorted dict    r  in dict r  for r in sorted in dict  key in dict get  reverse True     example above   sorted d    r  d r  for r in sorted d  key d get  key3    reverse True

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Python dicts are not sorted  by definition   You cannot sort one  nor control the order of its elements by how you insert them   You might want to look at collections OrderDict  which even comes with a little tutorial for almost exactly what you re trying to do  http   docs python org 2 library collections html ordereddict-examples-and-recipes

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A short example to sort dictionary is desending order for Python3   a1     a  1   b  13   d  4   c  2   e  30  a1 sorted keys   sorted a1  key a1 get  reverse True  for r in a1 sorted keys      print r  a1 r     Following will be the output  e 30 b 13 d 4 c 2 a 1

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List  dict     Neetu  22  Shiny  21  Poonam  23  print sorted dict items    sv   sorted dict values    print sv   Dictionary  d      l   len sv  while l    0       d append sv l - 1       l   l - 1 print d

User · Answer

You can use the operator to sort the dictionary by values in descending order   import operator  d     a  1   b  2   c  3  cd   sorted d items   key operator itemgetter 1  reverse True    The Sorted dictionary will look like   cd     c  3   b  2   a  1    Here  operator itemgetter 1  takes the value of the key which is at the index 1

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Whenever one has a dictionary where the values are integers  the Counter data structure is often a better choice to represent the data than a dictionary  If you already have a dictionary  a counter can easily be formed by  c   Counter d  123     as an example from your data  The most common function allows easy access to descending order of the items in the counter The more complete writeup on the Counter data structure is at https   docs python org 2 library collections html

User · Answer

Dictionaries do not have any inherent order  Or  rather  their inherent order is  arbitrary but not random   so it doesn t do you any good   In different terms  your d and your e would be exactly equivalent dictionaries   What you can do here is to use an OrderedDict   from collections import OrderedDict d      123      key1   3   key2   11   key3   3           124      key1   6   key2   56   key3   6           125      key1   7   key2   44   key3   9          d ascending   OrderedDict sorted d items    key lambda kv  kv 1   key3     d descending   OrderedDict sorted d items                                       key lambda kv  kv 1   key3    reverse True     The original d has some arbitrary order  d ascending has the order you thought you had in your original d  but didn t  And d descending has the order you want for your e     If you don t really need to use e as a dictionary  but you just want to be able to iterate over the elements of d in a particular order  you can simplify this   for key  value in sorted d items    key lambda kv  kv 1   key3    reverse True       do something with key  value      If you want to maintain a dictionary in sorted order across any changes  instead of an OrderedDict  you want some kind of sorted dictionary  There are a number of options available that you can find on PyPI  some implemented on top of trees  others on top of an OrderedDict that re-sorts itself as necessary  etc

User · Answer

you can make use of the below code for sorting in descending order and storing to a dictionary           listname                for key  value in sorted dictionaryName iteritems    key lambda  k v    v k  reverse True                 diction    value  value   key  key                listname append diction

[python] python dictionary sorting in descending order based on values

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