How to merge multiple dicts with same key or different key

Question

I have multiple dicts key-value pairs like this     d1    key1  x1  key2  y1    d2    key1  x2  key2  y2      I want the result to be a new dict  in most efficient way  if possible      d    key1   x1  x2   key2   y1  y2       Actually  I want result d to be     d    key1   x1 x1attrib  x2 x2attrib   key2   y1 y1attrib  y2 y2attrib       If somebody shows me how to get the first result  I can figure out the rest

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This library helped me  I had a dict list of nested keys with the same name but with different values  every other solution kept overriding those nested keys  https   pypi org project deepmerge  from deepmerge import always merger  def process parms args       temp list          for x in args          with open x   r   as stream              temp list append yaml safe load stream        return always merger merge  temp list

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Assume that you have the list of ALL keys  you can get this list by iterating through all dictionaries and get their keys   Let s name it listKeys  Also   listValues is the list of ALL values for a single key that you want to merge  allDicts  all dictionaries that you want to merge   result      for k in listKeys      listValues       we will convert it to tuple later  if you want      for d in allDicts         try              fileList append d k    try to append more values to a single key         except              pass     if listValues   if it is not empty         result k    typle listValues   convert to tuple  add to new dictionary with key k

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This function merges two dicts even if the keys in the two dictionaries are different  def combine dict d1  d2       combined          for k in set d1 keys      set d2 keys             combined k    tuple d k  for d in  d1  d2  if k in d      return combined  Example  d1          a   1       b   2    d2           b    boat        c    car     combine dict d1  d2    Returns          a    1          b    2   boat          c     car

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Python 3 x Update  From Eli Bendersky answer   Python 3 removed dict iteritems use dict items instead   See Python wiki  https   wiki python org moin Python3 0  from collections import defaultdict  dd   defaultdict list   for d in  d1  d2       for key  value in d items            dd key  append value

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Here s a general solution that will handle an arbitrary amount of dictionaries  with cases when keys are in only some of the dictionaries   from collections import defaultdict  d1    1  2  3  4  d2    1  6  3  7   dd   defaultdict list   for d in  d1  d2     you can list as many input dicts as you want here     for key  value in d items            dd key  append value   print dd    Shows   defaultdict  lt type  list  gt    1   2  6   3   4  7      Also  to get your  attrib  just change append value  to append value attrib

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If you only have d1 and d2   from collections import defaultdict  d   defaultdict list  for a  b in d1 items     d2 items        d a  append b

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A compact possibility  d1   a  1  b  2  d2   c  3  d  4  context    d1    d2  context   b   2   c   3   d   4   a   1

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assuming all keys are always present in all dicts   ds    d1  d2  d      for k in d1 iterkeys        d k    tuple d k  for d in ds    Note  In Python 3 x use below code   ds    d1  d2  d      for k in d1 keys      d k    tuple d k  for d in ds    and if the dic contain numpy arrays   ds    d1  d2  d      for k in d1 keys      d k    np concatenate list d k  for d in ds

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dict1     m   2   n   4  dict2     n   3   m   1    Making sure that the keys are in the same order   dict2 sorted    i dict2 i  for i in dict1 keys     keys   dict1 keys   values   zip dict1 values    dict2 sorted values    dictionary   dict zip keys  values     gives      m    2  1    n    4  3

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If keys are nested  d1      key1      nkey1    x1      key2      nkey2    y1       d2      key1      nkey1    x2      key2      nkey2    y2       ds    d1  d2  d      for k in d1 keys        for k2 in d1 k  keys            d setdefault k              d k  setdefault k2              d k  k2    tuple d k  k2  for d in ds   yields    key1     nkey1     x1    x2      key2     nkey2     y1    y2

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From blubb answer   You can also directly form the tuple using values from each list  ds    d1  d2  d      for k in d1 keys      d k     d1 k   d2 k     This might be useful if you had a specific ordering for your tuples  ds    d1  d2  d3  d4  d      for k in d1 keys      d k     d3 k   d1 k   d4 k   d2 k    if you wanted tuple in order of d3  d1  d4  d2

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Here is one approach you can use which would work even if both dictonaries don t have same keys   d1     a   test   b   btest   d   dreg   d2     a   cool   b   main   c   clear    d       for key in set d1 keys     d2 keys         try          d setdefault key     append d1 key               except KeyError          pass      try          d setdefault key     append d2 key                 except KeyError          pass  print d   This would generate below input     a     test    cool     c     clear     b     btest    main     d     dreg

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Assuming there are two dictionaries with exact same keys  below is the most succinct way of doing it  python3 should be used for both the solution    d1     a   1   b   2   c  3  d2     a   5   b   6   c  7      get keys from one of the dictionary ks    k for k in d1 keys     print ks    a    b    c      call values from each dictionary on available keys d merged    k   d1 k   d2 k   for k in ks   print d merged    a    1  5    b    2  6    c    3  7      to merge values as list d merged    k   d1 k   d2 k   for k in ks  print d merged    a    1  5    b    2  6    c    3  7     If there are two dictionaries with some common keys  but a few different keys  a list of all the keys should be prepared   d1     a   1   b   2   c  3   d   9  d2     a   5   b   6   c  7   e   4      get keys from one of the dictionary d1 ks    k for k in d1 keys    d2 ks    k for k in d2 keys     all ks   set d1 ks   d2 ks   print all ks    a    b    c    d    e      call values from each dictionary on available keys d merged    k   d1 get k   d2 get k   for k in all ks   print d merged    d    9  None    a    1  5    b    2  6    c    3  7    e    None  4

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To supplement the two-list solutions  here is a solution for processing a single list   A sample list  NetworkX-related  manually formatted here for readability    ec num list      src  tgt   ec num  ec num    for src  tgt  ec num in G edges data True    print   nec num list  n    format ec num list   ec num list     82  433    1 1 1 1        82  433    1 1 1 2        22  182    1 1 1 27        22  3785    1 2 4 1        22  36    6 4 1 1        145  36    1 1 1 37        36  154    2 3 3 1        36  154    2 3 3 8        36  72    4 1 1 32              Note the duplicate values for the same edges  defined by the tuples    To collate those  values  to their corresponding  keys    from collections import defaultdict ec num collection   defaultdict list  for k  v in ec num list      ec num collection k  append v   print   nec num collection  n    format ec num collection items     ec num collection     82  433     1 1 1 1    1 1 1 2           lt  lt  grouped  values    22  182     1 1 1 27       22  3785     1 2 4 1       22  36     6 4 1 1       145  36     1 1 1 37       36  154     2 3 3 1    2 3 3 8            lt  lt  grouped  values    36  72     4 1 1 32             If needed  convert that list to dict   ec num collection dict    k v for k  v in zip ec num collection  ec num collection    print   nec num collection dict  n    format dict ec num collection      ec num collection dict      82  433     1 1 1 1    1 1 1 2       22  182     1 1 1 27       22  3785     1 2 4 1       22  36     6 4 1 1       145  36     1 1 1 37       36  154     2 3 3 1    2 3 3 8       36  72     4 1 1 32             References    this thread  How to merge multiple dicts with same key   Python docs  https   docs python org 3 7 library collections html collections defaultdict

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def merge d1  d2  merge       result   dict d1      for k v in d2 iteritems            if k in result              result k    merge result k   v          else              result k    v     return result  d1     a   1   b   2  d2     a   1   b   3   c   2  print merge d1  d2  lambda x  y  x y      a    1  1    c   2   b    2  3

[python] How to merge multiple dicts with same key or different key?

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