sorting dictionary python 3

Question

I m working on python 3 2 2  Breaking my head more than 3 hours to sort a dictionary by it s keys  I managed to make it a sorted list with 2 argument members  but can not make it a sorted dictionary in the end   This is what I ve figured   myDic  10   b   3  a   5  c   sorted list sorted myDic items    key lambda x  x 0     But no matter what I can not make a dictionary out of this sorted list  How do I do that  Thanks

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A modern and fast solution  for Python 3 7  May also work in some interpreters of Python 3 6   TLDR  To sort a dictionary by keys use   sorted dict    k  disordered k  for k in sorted disordered     Almost three times faster than the accepted answer  probably more when you include imports   Comment on the accepted answer  The example in the accepted answer instead of iterating over the keys only - with key parameter of sorted   or the default behaviour of dict iteration - iterates over tuples  key  value   which suprisingly turns out to be much slower than comparing the keys only and accessing dictionary elements in a list comprehension   How to sort by key in Python 3 7  The big change in Python 3 7 is that the dictionaries are now ordered by default    You can generate sorted dict using dict comprehensions  Using OrderedDict might still be preferable for the compatibility sake  Do not use sorted d items    without key    See   disordered    10   b   3   a   5   c      sort keys  then get values from original - fast sorted dict    k  disordered k  for k in sorted disordered      key   itemgetter - slower from operator import itemgetter key   itemgetter 0  sorted dict    k  v for k  v in sorted disordered items    key key      key   lambda - the slowest key   lambda item  item 0  sorted dict    k  v for k in sorted disordered items    key key      Timing results   Best for  k  d k  for k in sorted d    7 507327548999456 Best for  k  v for k  v in sorted d items    key key getter    12 031082626002899 Best for  k  v for k  v in sorted d items    key key lambda    14 22885995300021  Best for dict sorted d items    key key getter    11 209122000000207 Best for dict sorted d items    key key lambda    13 289728325995384 Best for dict sorted d items      14 231471302999125  Best for OrderedDict sorted d items    key key getter    16 609151654003654 Best for OrderedDict sorted d items    key key lambda    18 52622927199991 Best for OrderedDict sorted d items      19 436101284998585   Testing code   from timeit import repeat  setup code       from operator import itemgetter from collections import OrderedDict import random random seed 0  d    i  chr i  for i in  random randint 0  120  for repeat in range 120    key getter   itemgetter 0  key lambda   lambda item  item 0       cases           fast       k  d k  for k in sorted d           k  v for k  v in sorted d items    key key getter           k  v for k  v in sorted d items    key key lambda           slower      dict sorted d items    key key getter          dict sorted d items    key key lambda          dict sorted d items             the slowest       OrderedDict sorted d items    key key getter          OrderedDict sorted d items    key key lambda          OrderedDict sorted d items          for code in cases      times   repeat code  setup setup code  repeat 3      print f Best for  code    min times

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I like python numpy for this kind of stuff  eg   r readData   nsorted   np lexsort  r calls  r slow requests  r very slow requests  r stalled requests     I have an example of importing CSV data into a numpy and ordering by column priorities  https   github com unixunion toolbox blob master python csv-numpy py  Kegan

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Any modern solution to this problem   I worked around it with       order   sorted   job  priority   for job in self joblist        sorted joblist          while order          min priority   min order          for job in self joblist              if job  priority      min priority                  sorted joblist      job                   order remove min priority      self joblist   sorted joblist   The joblist is formatted as  joblist        priority    3   name     foo             priority    1   name     bar             Basically I create a list  order  with all the elements by which I want to sort the dict then I iterate this list and the dict  when I find the item on the dict I send it to a new dict and remove the item from  order     Seems to be working  but I suppose there are better solutions

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I m not sure whether this could help  but I had a similar problem and I managed to solve it  by defining an apposite function   def sor dic key diction       lista          diction2          for x in diction          lista append  x  diction x        lista sort key lambda x  x 0       for l in lista          diction2 l 0     l 1      return diction2   This function returns another dictionary with the same keys and relative values  but sorted by its keys  Similarly  I defined a function that could sort a dictionary by its values  I just needed to use x 1  instead of x 0  in the lambda function  I find this second function mostly useless  but one never can tell

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I don t think you want an OrderedDict  It sounds like you d prefer a SortedDict  that is a dict that maintains its keys in sorted order  The sortedcontainers module provides just such a data type  It s written in pure-Python  fast-as-C implementations  has 100  coverage and hours of stress   Installation is easy with pip   pip install sortedcontainers   Note that if you can t pip install then you can simply pull the source files from the open-source repository   Then you re code is simply   from sortedcontainers import SortedDict myDic   SortedDict  10   b   3  a   5  c    sorted list   list myDic keys      The sortedcontainers module also maintains a performance comparison with other popular implementations

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Sorting dictionaries by value using comprehensions  I think it s nice as 1 line and no need for functions or lambdas  a     b   foo    c   bar    e    baz   a    f a f  for f in sorted a  key a   getitem

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With Python 3 7 I could do this    gt  gt  gt  myDic  10   b   3  a   5  c    gt  gt  gt  sortDic   sorted myDic items     gt  gt  gt  print dict sortDic    3  a   5  c   10   b     If you want a list of tuples    gt  gt  gt  myDic  10   b   3  a   5  c    gt  gt  gt  sortDic   sorted myDic items     gt  gt  gt  print sortDic    3   a     5   c     10   b

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The accepted answer definitely works  but somehow miss an important point   The OP is asking for a dictionary sorted by it s keys this is just not really possible and not what OrderedDict is doing   OrderedDict is maintaining the content of the dictionary in insertion order  First item inserted  second item inserted  etc    gt  gt  gt  d   OrderedDict    gt  gt  gt  d  foo     1  gt  gt  gt  d  bar     2  gt  gt  gt  d OrderedDict    foo   1     bar   2      gt  gt  gt  d   OrderedDict    gt  gt  gt  d  bar     2  gt  gt  gt  d  foo     1  gt  gt  gt  d OrderedDict    bar   2     foo   1      Hencefore I won t really be able to sort the dictionary inplace  but merely to create a new dictionary where insertion order match key order  This is explicit in the accepted answer where the new dictionary is b   This may be important if you are keeping access to dictionaries through containers  This is also important if you itend to change the dictionary later by adding or removing items  they won t be inserted in key order but at the end of dictionary    gt  gt  gt  d   OrderedDict   foo   5   bar   8    gt  gt  gt  d OrderedDict    foo   5     bar   8     gt  gt  gt  d  alpha     2  gt  gt  gt  d OrderedDict    foo   5     bar   8     alpha   2      Now  what does mean having a dictionary sorted by it s keys   That makes no difference when accessing elements by keys  this only matter when you are iterating over items  Making that a property of the dictionary itself seems like overkill  In many cases it s enough to sort keys   when iterating   That means that it s equivalent to do    gt  gt  gt  d     foo   5   bar   8   gt  gt  gt  for k v in d iteritems    print k  v   on an hypothetical sorted by key dictionary or    gt  gt  gt  d     foo   5   bar   8   gt  gt  gt  for k  v in iter  k  d k   for k in sorted d keys      print k  v   Of course it is not hard to wrap that behavior in an object by overloading iterators and maintaining a sorted keys list  But it is likely overkill

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dict does not keep its elements  order  What you need is an OrderedDict  http   docs python org library collections html collections OrderedDict  edit  Usage example    gt  gt  gt  from collections import OrderedDict  gt  gt  gt  a     foo   1   bar   2   gt  gt  gt  a   foo   1   bar   2   gt  gt  gt  b   OrderedDict sorted a items      gt  gt  gt  b OrderedDict    bar   2     foo   1     gt  gt  gt  b  foo   1  gt  gt  gt  b  bar   2

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Maybe not that good but I ve figured this   def order dic dic       ordered dic        key ls sorted dic keys        for key in key ls          ordered dic key  dic key      return ordered dic

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Dictionaries are unordered by definition  What would be the main reason for ordering by key  A list of tuples created by the sort method can be used for whatever the need may have been  but changing the list of tuples back into a dictionary will return a random order   gt  gt  gt  myDic  10   b   3   a   5   c    gt  gt  gt  sorted myDic items      3   a     5   c     10   b     gt  gt  gt  print dict myDic items      10   b   3   a   5   c

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Python s ordinary dicts cannot be made to provide the keys elements in any specific order  For that  you could use the OrderedDict type from the collections module  Note that the OrderedDict type merely keeps a record of insertion order  You would have to sort the entries prior to initializing the dictionary if you want subsequent views iterators to return the elements in order every time  For example    gt  gt  gt  myDic  10   b   3  a   5  c    gt  gt  gt  sorted list sorted myDic items    key lambda x  x 0    gt  gt  gt  myOrdDic   OrderedDict sorted list   gt  gt  gt  myOrdDic items     3   a     5   c     10   b     gt  gt  gt  myOrdDic 7     d   gt  gt  gt  myOrdDic items     3   a     5   c     10   b     7   d      If you want to maintain proper ordering for newly added items  you really need to use a different data structure  e g   a binary tree heap  This approach of building a sorted list and using it to initialize a new OrderedDict   instance is just woefully inefficient unless your data is completely static   Edit  So  if the object of sorting the data is merely to print it in order  in a format resembling a python dict object  something like the following should suffice   def pprint dict d       strings          for k in sorted d iterkeys             strings append   d    s      k  d k        return            join strings          Note that this function is not flexible w r t the types of the key  value pairs  i e   it expects the keys to be integers and the corresponding values to be strings   If you need more flexibility  use something like strings append   s   s     repr k   repr d k     instead

[python] sorting dictionary python 3

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