Get the key corresponding to the minimum value within a dictionary

Question

If I have a Python dictionary  how do I get the key to the entry which contains the minimum value   I was thinking about something to do with the min   function     Given the input    320 1  321 0  322 3    It would return 321

User · Answer

gt  gt  gt  d    320 1  321 0  322 3   gt  gt  gt  min d  key lambda k  d k    321

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Best  min d  key d get  -- no reason to interpose a useless lambda indirection layer or extract items or keys

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Here s an answer that actually gives the solution the OP asked for    gt  gt  gt  d    320 1  321 0  322 3   gt  gt  gt  d items     320  1    321  0    322  3    gt  gt  gt    find the minimum by comparing the second element of each tuple  gt  gt  gt  min d items    key lambda x  x 1     321  0    Using d iteritems   will be more efficient for larger dictionaries  however

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Use min with an iterator  for python 3 use items instead of iteritems   instead of lambda use the itemgetter from operator  which is faster than lambda   from operator import itemgetter min key      min d iteritems    key itemgetter 1

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to create an orderable class you have to override 6 special functions  so that it would be called by the min   function  these methods are  lt       le      gt      ge      eq       ne   in order they are less than  less than or equal  greater than  greater than or equal  equal  not equal  for example you should implement   lt   as follows   def   lt   self  other     return self comparable value  lt  other comparable value   then you can use the min function as follows   minValue   min yourList  key  lambda k  yourList k      this worked for me

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For the case where you have multiple minimal keys and want to keep it simple  def minimums some dict       positions        output variable     min value   float  inf       for k  v in some dict items            if v    min value              positions append k          if v  lt  min value              min value   v             positions        output variable             positions append k       return positions  minimums   a  1   b  2   c  -1   d  0   e  -1      e    c

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python  d  320 1  321 0  322 3  reduce lambda x y  x if d x  lt  d y  else y  d iterkeys      321

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Is this what you are looking for   d   dict   d 15 0   fifteen  d 14 0   fourteen  d 14 5   fourteenandhalf   print d min d keys       Prints  fourteen

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I compared how the following three options perform       import random  datetime  myDict      for i in range  10000000        myDict  i     random randint  0  10000000        OPTION 1  start   datetime datetime now    sorted      for i in myDict      sorted append    i  myDict  i       sorted sort  key   lambda x  x 1    print  sorted 0  0     end   datetime datetime now   print  end - start        OPTION 2  start   datetime datetime now    myDict values   list  myDict values     myDict keys   list  myDict keys     min value   min  myDict values   print  myDict keys  myDict values index  min value        end   datetime datetime now   print  end - start        OPTION 3  start   datetime datetime now    print  min  myDict  key myDict get      end   datetime datetime now   print  end - start     Sample output    option 1 236230 0 00 14 136808   option 2 236230 0 00 00 458026   option 3 236230 0 00 00 824048

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min zip d values    d keys     1    Use the zip function to create an iterator of tuples containing values and keys   Then wrap it with a min function which takes the minimum based on the first key   This returns a tuple containing  value  key  pair   The index of  1  is used to get the corresponding key

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min d items    key lambda x  x 1   0

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Edit  this is an answer to the OP s original question about the minimal key  not the minimal answer     You can get the keys of the dict using the keys function  and you re right about using min to find the minimum of that list

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Another approach to addressing the issue of multiple keys with the same min value    gt  gt  gt  dd    320 1  321 0  322 3  323 0   gt  gt  gt   gt  gt  gt  from itertools import groupby  gt  gt  gt  from operator import itemgetter  gt  gt  gt   gt  gt  gt  print  v for k v in groupby sorted  v k  for k v in dd iteritems     key itemgetter 0   next   1    321  323

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d    d 320  1 d 321  0 d 322  3 value   min d values    for k in d keys         if d k     value          print k d k

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If you are not sure that you have not multiple minimum values  I would suggest   d    320 1  321 0  322 3  323 0  print      join str key  for min value in  min d values      for key in d if d key   min value      Output  321  323

User · Answer

For multiple keys which have equal lowest value  you can use a list comprehension   d    320 1  321 0  322 3  323 0   minval   min d values    res    k for k  v in d items   if v  minval    321  323    An equivalent functional version   res   list filter lambda x  d x   minval  d

[python] Get the key corresponding to the minimum value within a dictionary

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