How do I sort a dictionary by value

Question

I have a dictionary of values read from two fields in a database  a string field and a numeric field  The string field is unique  so that is the key of the dictionary   I can sort on the keys  but how can I sort based on the values   Note  I have read Stack Overflow question here How do I sort a list of dictionaries by a value of the dictionary  and probably could change my code to have a list of dictionaries  but since I do not really need a list of dictionaries I wanted to know if there is a simpler solution to sort either in ascending or descending order

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For the sake of completeness  I am posting a solution using heapq  Note  this method will work for both numeric and non-numeric values   gt  gt  gt  x    1  2  3  4  4 3  2 1  0 0   gt  gt  gt  x items   x items    gt  gt  gt  heapq heapify x items   gt  gt  gt   To sort in reverse order  gt  gt  gt  heapq nlargest len x items  x items  operator itemgetter 1     3  4    4  3    1  2    2  1    0  0    gt  gt  gt   To sort in ascending order  gt  gt  gt  heapq nsmallest len x items  x items  operator itemgetter 1     0  0    2  1    1  2    4  3    3  4

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As of Python 3 6 the built-in dict will be ordered  Good news  so the OP s original use case of mapping pairs retrieved from a database with unique string ids as keys and numeric values as values into a built-in Python v3 6  dict  should now respect the insert order   If say the resulting two column table expressions from a database query like   SELECT a key  a value FROM a table ORDER BY a value    would be stored in two Python tuples  k seq and v seq  aligned by numerical index and with the same length of course   then   k seq     foo    bar    baz   v seq    0  1  42  ordered map   dict zip k seq  v seq     Allow to output later as   for k  v in ordered map items        print k  v    yielding in this case  for the new Python 3 6  built-in dict     foo 0 bar 1 baz 42   in the same ordering per value of v   Where in the Python 3 5 install on my machine it currently yields   bar 1 foo 0 baz 42   Details   As proposed in 2012 by Raymond Hettinger  cf  mail on python-dev with subject  More compact dictionaries with faster iteration   and now  in 2016  announced in a mail by Victor Stinner to python-dev with subject  Python 3 6 dict becomes compact and gets a private version  and keywords become ordered  due to the fix implementation of issue 27350  Compact and ordered dict  in Python 3 6 we will now be able  to use a built-in dict to maintain insert order    Hopefully this will lead to a thin layer OrderedDict implementation as a first step  As  JimFasarakis-Hilliard indicated  some see use cases for the OrderedDict type also in the future  I think the Python community at large will carefully inspect  if this will stand the test of time  and what the next steps will be   Time to rethink our coding habits to not miss the possibilities opened by stable ordering of    Keyword arguments and  intermediate  dict storage   The first because it eases dispatch in the implementation of functions and methods in some cases   The second as it encourages to more easily use dicts as intermediate storage in processing pipelines   Raymond Hettinger kindly provided documentation explaining  The Tech Behind Python 3 6 Dictionaries  - from his San Francisco Python Meetup Group presentation 2016-DEC-08   And maybe quite some Stack Overflow high decorated question and answer pages will receive variants of this information and many high quality answers will require a per version update too   Caveat Emptor  but also see below update 2017-12-15    As  ajcr rightfully notes   The order-preserving aspect of this new implementation is considered an implementation detail and should not be relied upon    from the whatsnew36  not nit picking  but the citation was cut a bit pessimistic  -   It continues as    this may change in the future  but it is desired to have this new dict implementation in the language for a few releases before changing the language spec to mandate order-preserving semantics for all current and future Python implementations  this also helps preserve backwards-compatibility with older versions of the language where random iteration order is still in effect  e g  Python 3 5     So as in some human languages  e g  German   usage shapes the language  and the will now has been declared     in whatsnew36   Update 2017-12-15   In a mail to the python-dev list  Guido van Rossum declared      Make it so   Dict keeps insertion order  is the ruling  Thanks     So  the version 3 6 CPython side-effect of dict insertion ordering is now becoming part of the language spec  and not anymore only an implementation detail   That mail thread also surfaced some distinguishing design goals for collections OrderedDict as reminded by Raymond Hettinger during discussion

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Of course  remember  you need to use OrderedDict because regular Python dictionaries don t keep the original order    from collections import OrderedDict a   OrderedDict sorted originalDict items    key lambda x  x 1        If you do not have Python 2 7 or higher  the best you can do is iterate over the values in a generator function   There is an OrderedDict for 2 4 and 2 6  here  but   a  I don t know about how well it works   and   b  You have to download and install it of course  If you do not have administrative access  then I m afraid the option s out      def gen originalDict       for x  y in sorted zip originalDict keys    originalDict values     key lambda z  z 1            yield  x  y       Yields as a tuple with  key  value   You can iterate with conditional clauses to get what you want    for bleh  meh in gen myDict       if bleh     foo           print myDict bleh       You can also print out every value  for bleh  meh in gen myDict       print bleh  meh    Please remember to remove the parentheses after print if not using Python 3 0 or above

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Because of requirements to retain backward compatability with older versions of Python I think the OrderedDict solution is very unwise  You want something that works with Python 2 7 and older versions   But the collections solution mentioned in another answer is absolutely superb  because you retrain a connection between the key and value which in the case of dictionaries is extremely important   I don t agree with the number one choice presented in another answer  because it throws away the keys   I used the solution mentioned above  code shown below  and retained access to both keys and values and in my case the ordering was on the values  but the importance was the ordering of the keys after ordering the values   from collections import Counter  x     hello  1   python  5   world  3  c Counter x  print c most common      gt  gt     python   5     world   3     hello   1

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This works in 3 1 x   import operator slovar sorted sorted slovar items    key operator itemgetter 1   reverse True  print slovar sorted

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If your values are integers  and you use Python 2 7 or newer  you can use collections Counter instead of dict  The most common method will give you all items  sorted by the value

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You can create an  inverted index   also  from collections import defaultdict inverse  defaultdict  list   for k  v in originalDict items        inverse v  append  k     Now your inverse has the values  each value has a list of applicable keys   for k in sorted inverse       print k  inverse k

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In recent Python 2 7  we have the new OrderedDict type  which remembers the order in which the items were added    gt  gt  gt  d     third   3   first   1   fourth   4   second   2    gt  gt  gt  for k  v in d items            print   s   s     k  v      second  2 fourth  4 third  3 first  1   gt  gt  gt  d   second   2   fourth   4   third   3   first   1    To make a new ordered dictionary from the original  sorting by the values    gt  gt  gt  from collections import OrderedDict  gt  gt  gt  d sorted by value   OrderedDict sorted d items    key lambda x  x 1      The OrderedDict behaves like a normal dict    gt  gt  gt  for k  v in d sorted by value items            print   s   s     k  v      first  1 second  2 third  3 fourth  4   gt  gt  gt  d sorted by value OrderedDict    first   1     second   2     third   3     fourth   4

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You could use   sorted d items    key lambda x  x 1     This will sort the dictionary by the values of each entry within the dictionary from smallest to largest   To sort it in descending order just add reverse True   sorted d items    key lambda x  x 1   reverse True    Input   d     one  1  three  3  five  5  two  2  four  4  a   sorted d items    key lambda x  x 1       print a    Output      one   1     two   2     three   3     four   4     five   5

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Iterate through a dict and sort it by its values in descending order     python --version Python 3 2 2    cat sort dict by val desc py  dictionary   dict siis   1  sana   2  joka   3  tuli   4  aina   5  for word in sorted dictionary  key dictionary get  reverse True     print word  dictionary word      python sort dict by val desc py  aina 5 tuli 4 joka 3 sana 2 siis 1

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Here is a solution using zip on d values   and d keys     A few lines down this link  on Dictionary view objects  is      This allows the creation of  value  key  pairs using zip    pairs   zip d values    d keys       So we can do the following   d     key1   874 7   key2   5   key3   8 1   d sorted   sorted zip d values    d keys      print d sorted    prints    5   key2     8 1   key3     874 7   key1

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It can often be very handy to use namedtuple  For example  you have a dictionary of  name  as keys and  score  as values and you want to sort on  score    import collections Player   collections namedtuple  Player    score name   d     John  5   Alex  10   Richard   7    sorting with lowest score first   worst   sorted Player v k  for  k v  in d items      sorting with highest score first   best   sorted  Player v k  for  k v  in d items     reverse True    Now you can get the name and score of  let s say the second-best player  index 1  very Pythonically like this   player   best 1  player name      Richard  player score     7

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from django utils datastructures import SortedDict  def sortedDictByKey self data          Sorted dictionary order by key        sortedDict   SortedDict       if data          if isinstance data  dict               sortedKey   sorted data keys                for k in sortedKey                  sortedDict k    data k      return sortedDict

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Starting from Python 3 6  dict objects are now ordered by insertion order  It s officially in the specs of Python 3 7    gt  gt  gt  words     python   2   blah   4   alice   3   gt  gt  gt  dict sorted words items    key lambda x  x 1      python   2   alice   3   blah   4    Before that  you had to use OrderedDict   Python 3 7 documentation says      Changed in version 3 7  Dictionary order is guaranteed to be insertion   order  This behavior was implementation detail of CPython from 3 6

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As simple as  sorted dict1  key dict1 get   Well  it is actually possible to do a  sort by dictionary values   Recently I had to do that in a Code Golf  Stack Overflow question Code golf  Word frequency chart   Abridged  the problem was of the kind  given a text  count how often each word is encountered and display a list of the top words  sorted by decreasing frequency    If you construct a dictionary with the words as keys and the number of occurrences of each word as value  simplified here as   from collections import defaultdict d   defaultdict int  for w in text split        d w     1   then you can get a list of the words  ordered by frequency of use with sorted d  key d get  - the sort iterates over the dictionary keys  using the number of word occurrences as a sort key     for w in sorted d  key d get  reverse True       print w  d w     I am writing this detailed explanation to illustrate what people often mean by  I can easily sort a dictionary by key  but how do I sort by value  - and I think the original post was trying to address such an issue  And the solution is to do sort of list of the keys  based on the values  as shown above

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Python 3 7  or CPython 3 6 Dicts preserve insertion order in Python 3 7   Same in CPython 3 6  but it s an implementation detail   gt  gt  gt  x    1  2  3  4  4  3  2  1  0  0   gt  gt  gt   k  v for k  v in sorted x items    key lambda item  item 1     0  0  2  1  1  2  4  3  3  4   or  gt  gt  gt  dict sorted x items    key lambda item  item 1     0  0  2  1  1  2  4  3  3  4   Older Python It is not possible to sort a dictionary  only to get a representation of a dictionary that is sorted  Dictionaries are inherently orderless  but other types  such as lists and tuples  are not  So you need an ordered data type to represent sorted values  which will be a list   probably a list of tuples  For instance  import operator x    1  2  3  4  4  3  2  1  0  0  sorted x   sorted x items    key operator itemgetter 1    sorted x will be a list of tuples sorted by the second element in each tuple  dict sorted x     x  And for those wishing to sort on keys instead of values  import operator x    1  2  3  4  4  3  2  1  0  0  sorted x   sorted x items    key operator itemgetter 0    In Python3 since unpacking is not allowed we can use x    1  2  3  4  4  3  2  1  0  0  sorted x   sorted x items    key lambda kv  kv 1    If you want the output as a dict  you can use collections OrderedDict  import collections  sorted dict   collections OrderedDict sorted x

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This method will not use lambda and works well on Python 3 6      sort dictionary by value d     a1    fsdfds    g5    aa3432ff    ca   zz23432   def getkeybyvalue d i       for k  v in d items            if v    i              return  k   sortvaluelist   sorted d values       In  gt  gt  Python 3 6   lt  lt  the INSERTION-ORDER of a dict is preserved  That is    when creating a NEW dictionary and filling it  in sorted order     that order will be maintained  sortresult     for i1 in sortvaluelist         key   getkeybyvalue d i1      sortresult key    i1 print        sort by value        print  sortresult  print

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In Python 2 7  simply do   from collections import OrderedDict   regular unsorted dictionary d     banana   3   apple  4   pear   1   orange   2     dictionary sorted by key OrderedDict sorted d items    key lambda t  t 0    OrderedDict    apple   4     banana   3     orange   2     pear   1       dictionary sorted by value OrderedDict sorted d items    key lambda t  t 1    OrderedDict    pear   1     orange   2     banana   3     apple   4      copy-paste from   http   docs python org dev library collections html ordereddict-examples-and-recipes  Enjoy  -

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You can also use custom function that can be passed to key   def dict val x       return x 1  x    1  2  3  4  4  3  2  1  0  0  sorted x   sorted x items    key dict val

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UPDATE  5 DECEMBER 2015 using Python 3 5  Whilst I found the accepted answer useful  I was also surprised that it hasn t been updated to reference OrderedDict from the standard library collections module as a viable  modern alternative - designed to solve exactly this type of problem   from operator import itemgetter from collections import OrderedDict  x    1  2  3  4  4  3  2  1  0  0  sorted x   OrderedDict sorted x items    key itemgetter 1      OrderedDict   0  0    2  1    1  2    4  3    3  4      The official OrderedDict documentation offers a very similar example too  but using a lambda for the sort function     regular unsorted dictionary d     banana   3   apple  4   pear   1   orange   2     dictionary sorted by value OrderedDict sorted d items    key lambda t  t 1      OrderedDict    pear   1     orange   2     banana   3     apple   4

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months     January   31   February   28   March   31   April   30   May   31             June   30   July   31   August   31   September   30   October   31             November   30   December   31   def mykey t           Customize your sorting logic using this function   The parameter to     this function is a tuple   Comment uncomment the return statements to test     different logics              return t 1                 sort by number of days in the month      return t 1   t 0          sort by number of days  then by month name      return len t 0            sort by length of month name      return t 0  -1            sort by last character of month name     Since a dictionary can t be sorted by value  what you can do is to convert   it into a list of tuples with tuple length 2    You can then do custom sorts by passing your own function to sorted    months as list   sorted months items    key mykey  reverse False   for month in months as list      print month

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You can use a skip dict which is a dictionary that s permanently sorted by value    gt  gt  gt  data    1  2  3  4  4  3  2  1  0  0   gt  gt  gt  SkipDict data   0  0 0  2  1 0  1  2 0  4  3 0  3  4 0    If you use keys    values   or items   then you ll iterate in sorted order by value   It s implemented using the skip list datastructure

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As pointed out by Dilettant  Python 3 6 will now keep the order  I thought I d share a function I wrote that eases the sorting of an iterable  tuple  list  dict   In the latter case  you can sort either on keys or values  and it can take numeric comparison into account  Only for  gt   3 6  When you try using sorted on an iterable that holds e g  strings as well as ints  sorted   will fail  Of course you can force string comparison with str    However  in some cases you want to do actual numeric comparison where 12 is smaller than 20  which is not the case in string comparison   So I came up with the following  When you want explicit numeric comparison you can use the flag num as num which will try to do explicit numeric sorting by trying to convert all values to floats  If that succeeds  it will do numeric sorting  otherwise it ll resort to string comparison  Comments for improvement welcome  def sort iterable iterable  sort on None  reverse False  num as num False       def  sort i           sort by 0   keys  1 values  None for lists and tuples       try          if num as num            if i is None               sorted   sorted iterable  key lambda v  float v   reverse reverse            else               sorted   dict sorted iterable items    key lambda v  float v i    reverse reverse           else            raise TypeError       except  TypeError  ValueError           if i is None             sorted   sorted iterable  key lambda v  str v   reverse reverse          else             sorted   dict sorted iterable items    key lambda v  str v i    reverse reverse                return  sorted            if isinstance iterable  list         sorted list    sort None        return sorted list     elif isinstance iterable  tuple         sorted list   tuple  sort None         return sorted list     elif isinstance iterable  dict         if sort on     keys           sorted dict    sort 0          return sorted dict       elif sort on     values           sorted dict    sort 1          return sorted dict       elif sort on is not None          raise ValueError f quot Unexpected value  sort on  for sort on  When sorting a dict  use key or values quot       else        raise TypeError f quot Unexpected type  type iterable   for iterable  Expected a list  tuple  or dict quot

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Using Python 3 2   x     b  4   a  3   c  1  for i in sorted x values         print list x keys    list x values    index i

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Pretty much the same as Hank Gay s answer   sorted   value key  for  key value  in mydict items       Or optimized slightly as suggested by John Fouhy   sorted  value key  for  key value  in mydict items

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If values are numeric you may also use Counter from collections   from collections import Counter  x     hello   1   python   5   world   3  c   Counter x  print c most common      gt  gt     python   5     world   3     hello   1

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Try the following approach  Let us define a dictionary called mydict with the following data   mydict     carl  40             alan  2             bob  1             danny  3    If one wanted to sort the dictionary by keys  one could do something like   for key in sorted mydict iterkeys         print   s   s     key  mydict key     This should return the following output   alan  2 bob  1 carl  40 danny  3   On the other hand  if one wanted to sort a dictionary by value  as is asked in the question   one could do the following   for key  value in sorted mydict iteritems    key lambda  k v    v k        print   s   s     key  value    The result of this command  sorting the dictionary by value  should return the following   bob  1 alan  2 danny  3 carl  40

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Just learned relevant skill from Python for Everybody   You may use a temporary list to help you to sort the dictionary    Assume dictionary to be  d     apple   500 1   banana   1500 2   orange   1 0   pineapple   789 0     create a temporary list tmp         iterate through the dictionary and append each tuple into the temporary list  for key  value in d items        tmptuple    value  key      tmp append tmptuple     sort the list in ascending order tmp   sorted tmp   print  tmp    If you want to sort the list in descending order  simply change the original sorting line to   tmp   sorted tmp  reverse True    Using list comprehension  the one liner would be    Assuming the dictionary looks like d     apple   500 1   banana   1500 2   orange   1 0   pineapple   789 0   One liner for sorting in ascending order print  sorted   v  k  for k  v in d items       One liner for sorting in descending order print  sorted   v  k  for k  v in d items     reverse True     Sample Output    Asending order   1 0   orange     500 1   apple     789 0   pineapple     1500 2   banana     Descending order   1500 2   banana     789 0   pineapple     500 1   apple     1 0   orange

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I had the same problem  and I solved it like this   WantedOutput   sorted MyDict  key lambda x   MyDict x       People who answer  It is not possible to sort a dict  did not read the question  In fact   I can sort on the keys  but how can I sort based on the values   clearly means that he wants a list of the keys sorted according to the value of their values    Please notice that the order is not well defined  keys with the same value will be in an arbitrary order in the output list

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Dicts can t be sorted  but you can build a sorted list from them   A sorted list of dict values   sorted d values      A list of  key  value  pairs  sorted by value   from operator import itemgetter sorted d items    key itemgetter 1

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Beside using builtin module etc  i try solve it manually      first i made a function whose job is to returning minimal value each items of the dict    def returnminDict  dct       dict items    dct items       list items   list dict items      init items   list items 0      for i in range len list items            if list items i  1   gt  init items 1              continue         else             init items   list items i      return init items   Second  now we have a function which return item that has minimal value  then i make a new dict then loop over the dict    def SelectDictSort  dct       new dict          while  dct          mindict   returnminDict  dct          new dict update dict  mindict              dct pop mindict 0       return new dict   i try this SelectDictSort  2  5  5  1  4  3  1  1  0  1  9  2  8  2   will return     0  1  1  1  5  1  8  2  9  2  4  3  2  5    Hmmm    i dont know which is correct but this what i have tried       updated code from retrun new dct to return new dict

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Use ValueSortedDict from dicts   from dicts sorteddict import ValueSortedDict d    1  2  3  4  4 3  2 1  0 0  sorted dict   ValueSortedDict d  print sorted dict items       0  0    2  1    1  2    4  3    3  4

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You can use the collections Counter  Note  this will work for both numeric and non-numeric values    gt  gt  gt  x    1  2  3  4  4 3  2 1  0 0   gt  gt  gt  from collections import Counter  gt  gt  gt   To sort in reverse order  gt  gt  gt  Counter x  most common     3  4    4  3    1  2    2  1    0  0    gt  gt  gt   To sort in ascending order  gt  gt  gt  Counter x  most common     -1    0  0    2  1    1  2    4  3    3  4    gt  gt  gt   To get a dictionary sorted by values  gt  gt  gt  from collections import OrderedDict  gt  gt  gt  OrderedDict Counter x  most common     -1   OrderedDict   0  0    2  1    1  2    4  3    3  4

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This is the code   import operator origin list           name    foo    rank   0   rofl   20000         name    Silly    rank   15   rofl   1000         name    Baa    rank   300   rofl   20         name    Zoo    rank   10   rofl   200         name    Penguin    rank   -1   rofl   10000    print   gt  gt  Original  gt  gt   for foo in origin list      print foo  print   n gt  gt  Rofl sort  gt  gt   for foo in sorted origin list  key operator itemgetter  rofl         print foo  print   n gt  gt  Rank sort  gt  gt   for foo in sorted origin list  key operator itemgetter  rank         print foo   Here are the results   Original    name    foo    rank   0   rofl   20000    name    Silly    rank   15   rofl   1000    name    Baa    rank   300   rofl   20    name    Zoo    rank   10   rofl   200    name    Penguin    rank   -1   rofl   10000    Rofl    name    Baa    rank   300   rofl   20    name    Zoo    rank   10   rofl   200    name    Silly    rank   15   rofl   1000    name    Penguin    rank   -1   rofl   10000    name    foo    rank   0   rofl   20000    Rank     name    Penguin    rank   -1   rofl   10000    name    foo    rank   0   rofl   20000    name    Zoo    rank   10   rofl   200    name    Silly    rank   15   rofl   1000    name    Baa    rank   300   rofl   20

[python] How do I sort a dictionary by value?

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