Rename a dictionary key

Question

Is there a way to rename a dictionary key  without reassigning its value to a new name and removing the old name key  and without iterating through dict key value  In case of OrderedDict  do the same  while keeping that key s position

User · Answer

A few people before me mentioned the  pop trick to delete and create a key in a one-liner   I personally find the more explicit implementation more readable   d     a   1   b   2  v   d  b   del d  b   d  c     v   The code above returns   a   1   c   2

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Using a check for newkey  oldkey  this way you can do   if newkey  oldkey        dictionary newkey    dictionary oldkey      del dictionary oldkey

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I am using  wim  s answer above  with dict pop   when renaming keys  but I found a gotcha   Cycling through the dict to change the keys  without separating the list of old keys completely from the dict instance  resulted in cycling new  changed keys into the loop  and missing some existing keys    To start with  I did it this way   for current key in my dict      new key   current key replace              fixed metadata new key    fixed metadata pop current key    I found that cycling through the dict in this way  the dictionary kept finding keys even when it shouldn t  i e   the new keys  the ones I had changed   I needed to separate the instances completely from each other to  a  avoid finding my own changed keys in the for loop  and  b  find some keys that were not being found within the loop for some reason   I am doing this now   current keys   list my dict keys    for current key in current keys      and so on      Converting the my dict keys   to a list was necessary to get free of the reference to the changing dict   Just using my dict keys   kept me tied to the original instance  with the strange side effects

User · Answer

Suppose you want to rename key k3 to k4   temp dict     k1   v1    k2   v2    k3   v3   temp dict  k4    temp dict pop  k3

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For a regular dict  you can use  mydict k new    mydict pop k old   This will move the item to the end of the dict  unless k new was already existing in which case it will overwrite the value in-place  For a Python 3 7  dict where you additionally want to preserve the ordering  the simplest is to rebuild an entirely new instance  For example  renaming key 2 to  two    gt  gt  gt  d    0 0  1 1  2 2  3 3   gt  gt  gt    quot two quot  if k    2 else k v for k v in d items     0  0  1  1   two   2  3  3   The same is true for an OrderedDict  where you can t use dict comprehension syntax  but you can use a generator expression  OrderedDict  k new if k    k old else k  v  for k  v in od items     Modifying the key itself  as the question asks for  is impractical because keys are hashable which usually implies they re immutable and can t be modified

User · Answer

I came up with this function which does not mutate the original dictionary  This function also supports list of dictionaries too   import functools from typing import Union  Dict  List   def rename dict keys      data  Union Dict  List Dict    old key  str  new key  str                This function renames dictionary keys       param data       param old key       param new key       return  Union Dict  List Dict               if isinstance data  dict           res    k  v for k  v in data items   if k    old key          try              res new key    data old key          except KeyError              raise KeyError                   cannot rename key as old key   s  is not present in data                    old key                       return res     elif isinstance data  list           return list              map                  functools partial                      rename dict keys  old key old key  new key new key                                    data                              raise ValueError  expected type List Dict  or Dict got   s  for data    type data

User · Answer

You can use this OrderedDict recipe written by Raymond Hettinger and modify it to add a rename method  but this is going to be a O N  in complexity   def rename self key new key       ind   self  keys index key    get the index of old key  O N  operation     self  keys ind    new key     replace old key with new key in self  keys     self new key    self key      add the new key  this is added at the end of self  keys     self  keys pop -1             pop the last item in self  keys   Example   dic   OrderedDict    a  1    b  2    c  3    print dic dic rename  a   foo   dic rename  b   bar   dic  d     5 dic rename  d   spam   for k v in  dic items        print k v   output   OrderedDict   a   1   b   2   c   3   foo 1 bar 2 c 3 spam 5

User · Answer

Other answers are pretty good But in python3 6  regular dict also has order  So it s hard to keep key s position in normal case   def rename old dict old name new name       new dict          for key value in zip old dict keys   old dict values             new key   key if key    old name else new name         new dict new key    old dict key      return new dict

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In case someone wants to rename all the keys at once providing a list with the new names   def rename keys dict   new keys                new keys  type List    must match length of dict                 dict     oldK  value        d1  oldK newK   maps old keys to the new ones        d1   dict  zip  list dict  keys     new keys                 d1 oldK     new key      return  d1 oldK   value for oldK  value in dict  items

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I have combined some answers from the above thread and come up with the solution below  Although it is simple it can be used as a building block for making more complex key updates from a dictionary  test dict     a   1   b   2   c   3  print test dict      a   1   b   2   c   3  prefix    up  def dict key update json file           new keys          old keys          for i  key value  in enumerate json file items             old keys append key          new keys append str prefix    key    i have updated by adding a prefix to the            key     for old key  new key in zip old keys new keys           print  old     new     format old key  new key           if new key  old key               json file new key    json file pop old key       return json file  test dict   dict key update test dict  print test dict      upa   1   upb   2   upc   3

User · Answer

In case  of  renaming  all dictionary  keys   target dict     k1   v1    k2   v2    k3   v3   new keys     k4   k5   k6    for key n key in zip target dict keys    new keys       target dict n key    target dict pop key

User · Answer

helloswift123 I like your function  Here is a modification to rename multiple keys in a single call     def rename d  keymap                param d  old dict      type d  dict      param keymap     keys from-keys  values to-keys  keymap       returns  new dict      rtype  dict             new dict          for key  value in zip d keys    d values             new key   keymap get key  key          new dict new key    d key      return new dict

User · Answer

In Python 3 6  onwards   I would go for the following one-liner  test     a   1   old   2   c   3  old k    old  new k    new  new v   4    optional  print dict  new k  new v  if k    old k else  k  v  for k  v in test items       which produces    a   1   new   4   c   3    May be worth noting that without the print statement the ipython console jupyter notebook present the dictionary in an order of their choosing

[python] Rename a dictionary key

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