Comparing two dictionaries and checking how many key value pairs are equal

Question

I have two dictionaries  but for simplification  I will take these two    gt  gt  gt  x   dict a 1  b 2   gt  gt  gt  y   dict a 2  b 2    Now  I want to compare whether each key  value pair in x has the same corresponding value in y  So I wrote this    gt  gt  gt  for x values  y values in zip x iteritems    y iteritems             if x values    y values              print  Ok   x values  y values         else              print  Not   x values  y values   And it works since a tuple is returned and then compared for equality   My questions   Is this correct  Is there a better way to do this  Better not in speed  I am talking about code elegance   UPDATE  I forgot to mention that I have to check how many key  value pairs are equal

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mouad  s answer is nice if you assume that both dictionaries contain simple values only  However  if you have dictionaries that contain dictionaries you ll get an exception as dictionaries are not hashable   Off the top of my head  something like this might work   def compare dictionaries dict1  dict2        if dict1 is None or dict2 is None          print  Nones           return False       if  not isinstance dict1  dict   or  not isinstance dict2  dict            print  Not dict           return False       shared keys   set dict1 keys     amp  set dict2 keys          if not   len shared keys     len dict1 keys    and len shared keys     len dict2 keys              print  Not all keys are shared           return False        dicts are equal   True      for key in dict1 keys             if isinstance dict1 key   dict  or isinstance dict2 key   dict                dicts are equal   dicts are equal and compare dictionaries dict1 key   dict2 key            else               dicts are equal   dicts are equal and all atleast 1d dict1 key     dict2 key          return dicts are equal

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To test if two dicts are equal in keys and values   def dicts equal d1 d2           return True if all keys and values are the same         return all k in d2 and d1 k     d2 k                 for k in d1            and all k in d1 and d1 k     d2 k                 for k in d2    If you want to return the values which differ  write it differently   def dict1 minus d2 d1  d2           return the subset of d1 where the keys don t exist in d2 or         the values in d2 are different  as a dict         return  k v for k v in d1 items   if k in d2 and v    d2 k     You would have to call it twice i e   dict1 minus d2 d1 d2  extend dict1 minus d2 d2 d1

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def dict compare d1  d2       d1 keys   set d1 keys        d2 keys   set d2 keys        shared keys   d1 keys intersection d2 keys      added   d1 keys - d2 keys     removed   d2 keys - d1 keys     modified    o    d1 o   d2 o   for o in shared keys if d1 o     d2 o       same   set o for o in shared keys if d1 o     d2 o       return added  removed  modified  same  x   dict a 1  b 2  y   dict a 2  b 2  added  removed  modified  same   dict compare x  y

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Why not just iterate through one dictionary and check the other in the process  assuming both dictionaries have the same keys     x   dict a 1  b 2  y   dict a 2  b 2   for key  val in x items        if val    y key           print   Ok   val  y key       else          print   Not   val  y key     Output   Not 1 2 Ok 2 2

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gt  gt  gt  hash 1   a    foo    b    bar    gt  gt  gt  hash 2   a    foo    b    bar    gt  gt  gt  set 1   set  hash 1 iteritems     gt  gt  gt  set 1 set    a    foo      b    bar      gt  gt  gt  set 2   set  hash 2 iteritems     gt  gt  gt  set 2 set    a    foo      b    bar      gt  gt  gt  len  set 1 difference set 2   0  gt  gt  gt  if  len set 1 difference set 2     len set 2 difference set 1       False         print  The two hashes match       The two hashes match   gt  gt  gt  hash 2  c      baz   gt  gt  gt  hash 2   a    foo    c    baz    b    bar    gt  gt  gt  if  len set 1 difference set 2     len set 2 difference set 1       False          print  The two hashes match        gt  gt  gt   gt  gt  gt  hash 2 pop  c    baz    Here s another option    gt  gt  gt  id hash 1  140640738806240  gt  gt  gt  id hash 2  140640738994848   So as you see the two id s are different  But the rich comparison operators seem to do the trick    gt  gt  gt  hash 1    hash 2 True  gt  gt  gt   gt  gt  gt  hash 2   a    foo    b    bar    gt  gt  gt  set 2   set  hash 2 iteritems     gt  gt  gt  if  len set 1 difference set 2     len set 2 difference set 1       False          print  The two hashes match       The two hashes match   gt  gt  gt

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dic1    dic2 From python docs   The following examples all return a dictionary equal  to   quot one quot   1   quot two quot   2   quot three quot   3    gt  gt  gt  a   dict one 1  two 2  three 3   gt  gt  gt  b     one   1   two   2   three   3   gt  gt  gt  c   dict zip   one    two    three     1  2  3     gt  gt  gt  d   dict    two   2     one   1     three   3     gt  gt  gt  e   dict   three   3   one   1   two   2    gt  gt  gt  a    b    c    d    e True    Providing keyword arguments as in the first example only works for keys that are valid Python identifiers  Otherwise  any valid keys can be used   Valid for both py2 and py3

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Here is my answer  use a recursize way   def dict equals da  db       if not isinstance da  dict  or not isinstance db  dict           return False     if len da     len db           return False     for da key in da          if da key not in db              return False         if not isinstance db da key   type da da key                 return False         if isinstance da da key   dict               res   dict equals da da key   db da key               if res is False                  return False         elif da da key     db da key               return False     return True  a    1  2 3   name    cc    dd    3 4  21  nm     b    1  2 3   name    cc    dd    3 4  21  nm     print dict equals a  b    Hope that helps

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Code def equal a  b       type a   type a      type b   type b           if type a    type b          return False          if isinstance a  dict           if len a     len b               return False         for key in a              if key not in b                  return False             if not equal a key   b key                    return False         return True      elif isinstance a  list           if len a     len b               return False         while len a               x   a pop               index   indexof x  b              if index    -1                  return False             del b index          return True              else          return a    b  def indexof x  a       for i in range len a            if equal x  a i                return i     return -1  Test  gt  gt  gt  a          number   1       list     one    two      gt  gt  gt  b          list     two    one         number   1    gt  gt  gt  equal a  b  True

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Since it seems nobody mentioned deepdiff  I will add it here for completeness  I find it very convenient for getting diff of  nested  objects in general   Installation  pip install deepdiff   Sample code  import deepdiff import json  dict 1          a   1       nested              b   1           dict 2          a   2       nested              b   2           diff   deepdiff DeepDiff dict 1  dict 2  print json dumps diff  indent 4     Output         values changed              root  a                    new value   2               old value   1                     root  nested    b                    new value   2               old value   1                     Note about pretty-printing the result for inspection  The above code works if both dicts have the same attribute keys  with possibly different attribute values as in the example   However  if an  extra  attribute is present is one of the dicts  json dumps   fails with  TypeError  Object of type PrettyOrderedSet is not JSON serializable   Solution  use diff to json   and json loads     json dumps   to pretty-print   import deepdiff import json  dict 1          a   1       nested              b   1              extra   3    dict 2          a   2       nested              b   2           diff   deepdiff DeepDiff dict 1  dict 2  print json dumps json loads diff to json     indent 4       Output          dictionary item removed              root  extra                values changed              root  a                    new value   2               old value   1                     root  nested    b                    new value   2               old value   1                     Alternative  use pprint  results in a different formatting   import pprint    same code as above  pprint pprint diff  indent 4    Output        dictionary item removed    root  extra          values changed        root  a          new value   2                                              old value   1                              root  nested    b          new value   2                                                        old value   1

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In PyUnit there s a method which compares dictionaries beautifully  I tested it using the following two dictionaries  and it does exactly what you re looking for   d1    1   value1         2     subKey1   subValue1               subKey2   subValue2     d2    1   value1         2     subKey2   subValue2               subKey1    subValue1              def assertDictEqual self  d1  d2  msg None           self assertIsInstance d1  dict   First argument is not a dictionary           self assertIsInstance d2  dict   Second argument is not a dictionary            if d1    d2              standardMsg     s     s     safe repr d1  True   safe repr d2  True               diff      n      n  join difflib ndiff                             pprint pformat d1  splitlines                               pprint pformat d2  splitlines                  standardMsg   self  truncateMessage standardMsg  diff              self fail self  formatMessage msg  standardMsg     I m not recommending importing unittest into your production code  My thought is the source in PyUnit could be re-tooled to run in production  It uses pprint which  pretty prints  the dictionaries  Seems pretty easy to adapt this code to be  production ready

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Yet another possibility  up to the last note of the OP  is to compare the hashes  SHA or MD  of the dicts dumped as JSON  The way hashes are constructed guarantee that if they are equal  the source strings are equal as well  This is very fast and mathematically sound    import json import hashlib  def hash dict d       return hashlib sha1 json dumps d  sort keys True   hexdigest    x   dict a 1  b 2  y   dict a 2  b 2  z   dict a 1  b 2   print hash dict x     hash dict y   print hash dict x     hash dict z

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A simple compare with    should be enough nowadays  python 3 8   Even when you compare the same dicts in a different order  last example   The best thing is  you don t need a third-party package to accomplish this   a     one    dog    two    cat    three    mouse   b     one    dog    two    cat    three    mouse    c     one    dog    two    cat    three    mouse   d     one    dog    two    cat    three    mouse    four    fish    e     one    cat    two    dog    three    mouse   f     one    dog    two    cat    three    mouse    g     two    cat    one    dog    three    mouse   h     one    dog    two    cat    three    mouse     print a    b    True print c    d    False print e    f    False print g    h    True

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Being late in my response is better than never   Compare Not Equal is more efficient than comparing Equal  As such two dicts are not equal if any key values in one dict is not found in the other dict  The code below takes into consideration that you maybe comparing default dict and thus uses get instead of getitem       Using a kind of random value as default in the get call equal to the key being retrieved - just in case the dicts has a None as value in one dict and that key does not exist in the other  Also the get    condition is checked before the not in condition for efficiency because you are doing the check on the keys and values from both sides at the same time   def Dicts Not Equal first second           return True if both do not have same length or if any keys and values are not the same         if len first     len second            for k in first              if first get k     second get k k  or k not in second  return  True          for k in second                       if first get k k     second get k  or k not in first  return  True          return  False         return  True

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In Python 3 6  It can be done as -  if  len dict 1   len dict 2      for i in dict 1 items            ret bool i in dict 2 items      ret variable will be true if all the items of dict 1 in present in dict 2

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see dictionary view objects  https   docs python org 2 library stdtypes html dict  This way you can subtract dictView2 from dictView1 and it will return a set of key value pairs that are different in dictView2   original     one  1  two  2  ACTION   ADD   originalView original viewitems   updatedDict     one  1  two  2  ACTION   REPLACE   updatedDictView updatedDict viewitems   delta original   updatedDict print delta  gt  gt set    ACTION    REPLACE       You can intersect  union  difference  shown above   symmetric difference these dictionary view objects  Better  Faster  - not sure  but part of the standard library - which makes it a big plus for portability

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gt  gt  gt  x     a  1  b  2  c  3   gt  gt  gt  x   a   1   b   2   c   3    gt  gt  gt  y     a  2  b  4  c  3   gt  gt  gt  y   a   2   b   4   c   3   METHOD 1    gt  gt  gt  common item   x items   amp y items    using union x item     gt  gt  gt  common item    c   3    METHOD 2     gt  gt  gt  for i in x items            if i in y items               print  true           else             print  false     false false true

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I m new to python but I ended up doing something similar to  mouad  unmatched item   set dict 1 items      set dict 2 items    len unmatched item    should be 0   The XOR operator     should eliminate all elements of the dict when they are the same in both dicts

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If you want to know how many values match in both the dictionaries  you should have said that      Maybe something like this   shared items    k  x k  for k in x if k in y and x k     y k   print len shared items

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The easiest way  and one of the more robust at that  to do a deep comparison of two dictionaries is to serialize them in JSON format  sorting the keys  and compare the string results  import json if json dumps x  sort keys True     json dumps y  sort keys True          Do something

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import json  if json dumps dict1     json dumps dict2       print  Equal

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Just use   assert cmp dict1  dict2     0

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What you want to do is simply x  y   What you do is not a good idea  because the items in a dictionary are not supposed to have any order  You might be comparing    a  1    b  1   with    b  1     a  1    same dictionaries  different order    For example  see this    gt  gt  gt  x   dict a 2  b 2 c 3  d 4   gt  gt  gt  x   a   2   c   3   b   2   d   4   gt  gt  gt  y   dict b 2 c 3  d 4   gt  gt  gt  y   c   3   b   2   d   4   gt  gt  gt  zip x iteritems    y iteritems        a   2     c   3       c   3     b   2       b   2     d   4      The difference is only one item  but your algorithm will see that all items are different

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for python3   data set a   dict a items   data set b   dict b items    difference set   data set a   data set b

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The function is fine IMO  clear and intuitive  But just to give you  another  answer  here is my go   def compare dict dict1  dict2       for x1 in dict1 keys            z   dict1 get x1     dict2 get x1          if not z              print  key   x1              print  value A   dict1 get x1     nvalue B   dict2 get x1               print  ----- n     Can be useful for you or for anyone else    EDIT   I have created a recursive version of the one above   Have not seen that in the other answers  def compare dict a  b         Compared two dictionaries         Posts things that are not equal       res compare          for k in set list a keys      list b keys              if isinstance a k   dict               z0   compare dict a k   b k           else              z0   a k     b k           z0 bool   np all z0          res compare append z0 bool          if not z0 bool              print k  a k   b k       return np all res compare

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I am using this solution that works perfectly for me in Python 3   import logging log   logging getLogger   name              def deep compare self left  right  level 0           if type left     type right               log info  Exit 1 - Different types               return False          elif type left  is dict                Dict comparison             for key in left                  if key not in right                      log info  Exit 2 - missing    in right  format key                       return False                 else                      if not deep compare left str key    right str key    level  1                            log info  Exit 3 - different children                           return False             return True         elif type left  is list                List comparison             for key in left                  if key not in right                      log info  Exit 4 - missing    in right  format key                       return False                 else                      if not deep compare left left index key    right right index key    level  1                            log info  Exit 5 - different children                           return False             return True         else                Other comparison             return left    right          return False    It compares dict  list and any other types that implements the      operator by themselves  If you need to compare something else different  you need to add a new branch in the  if tree    Hope that helps

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Below code will help you to compare list of dict in python   def compate generic types object1  object2       if isinstance object1  str  and isinstance object2  str           return object1    object2     elif isinstance object1  unicode  and isinstance object2  unicode           return object1    object2     elif isinstance object1  bool  and isinstance object2  bool           return object1    object2     elif isinstance object1  int  and isinstance object2  int           return object1    object2     elif isinstance object1  float  and isinstance object2  float           return object1    object2     elif isinstance object1  float  and isinstance object2  int           return object1    float object2      elif isinstance object1  int  and isinstance object2  float           return float object1     object2      return True  def deep list compare object1  object2       retval   True     count   len object1      object1   sorted object1      object2   sorted object2      for x in range count           if isinstance object1 x   dict  and isinstance object2 x   dict               retval   deep dict compare object1 x   object2 x               if retval is False                  print  Unable to match   0   element in list  format x                  return False         elif isinstance object1 x   list  and isinstance object2 x   list               retval   deep list compare object1 x   object2 x               if retval is False                  print  Unable to match   0   element in list  format x                  return False         else              retval   compate generic types object1 x   object2 x               if retval is False                  print  Unable to match   0   element in list  format x                  return False      return retval  def deep dict compare object1  object2       retval   True      if len object1     len object2           return False      for k in object1 iterkeys            obj1   object1 k          obj2   object2 k          if isinstance obj1  list  and isinstance obj2  list               retval   deep list compare obj1  obj2              if retval is False                  print  Unable to match   0    format k                  return False          elif isinstance obj1  dict  and isinstance obj2  dict               retval   deep dict compare obj1  obj2              if retval is False                  print  Unable to match   0    format k                  return False         else              retval   compate generic types obj1  obj2              if retval is False                  print  Unable to match   0    format k                  return False      return retval

[python] Comparing two dictionaries and checking how many (key, value) pairs are equal

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