enumerate for dictionary in python

Question

I know we use enumerate for iterating a list but I tried it in a dictionary and it didn t give an error   CODE   enumm    0  1  1  2  2  3  4  4  5  5  6  6  7  7   for i  j in enumerate enumm       print i  j    OUTPUT   0 0  1 1  2 2  3 4  4 5  5 6  6 7   Can someone explain the output

User · Answer

Since you are using enumerate hence your i is actually the index of the key rather than the key itself   So  you are getting 3 in the first column of the row 3 4even though there is no key 3   enumerate iterates through a data structure be it list or a dictionary  while also providing the current iteration number    Hence  the columns here are the iteration number followed by the key in dictionary enum  Others Solutions have already shown how to iterate over key and value pair so I won t repeat the same in mine

User · Answer

That sure must seem confusing  So this is what is going on  The first value of enumerate  in this case i  returns the next index value starting at 0 so 0  1  2  3      It will always return these numbers regardless of what is in the dictionary  The second value of enumerate  in this case j  is returning the values in your dictionary enumm  we call it a dictionary in Python   What you really want to do is what roadrunner66 responded with

User · Answer

Iterating over a Python dict means to iterate over its keys exactly the same way as with dict keys   The order of the keys is determined by the implementation code and you cannot expect some specific order      Keys and values are iterated over in an arbitrary order which is   non-random  varies across Python implementations  and depends on the   dictionary   s history of insertions and deletions  If keys  values and   items views are iterated over with no intervening modifications to the   dictionary  the order of items will directly correspond     That s why you see the indices 0 to 7 in the first column  They are produced by enumerate and are always in the correct order  Further you see the dict s keys 0 to 7 in the second column  They are not sorted

User · Answer

The first column of output is the index of each item in enumm and the second one is its keys  If you want to iterate your dictionary then use  items     for k  v in enumm items        print k  v    And the output should look like   0 1 1 2 2 3 4 4  5 5 6 6 7 7

User · Answer

Just thought I d add  if you d like to enumerate over the index  key  and values of a dictionary  your for loop should look like this   for index   key  value  in enumerate your dict items         print index  key  value

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You may find it useful to include index inside key  d     a   1   b   2  d     i  k   v for i   k  v  in enumerate d items      Output    0   a    True   1   b    False

User · Answer

On top of the already provided answers there is a very nice pattern in Python that allows you to enumerate both keys and values of a dictionary   The normal case you enumerate the keys of the dictionary   example dict    1  a   2  b   3  c   4  d    for i  k in enumerate example dict       print i  k    Which outputs   0 1 1 2 2 3 3 4   But if you want to enumerate through both keys and values this is the way   for i   k  v  in enumerate example dict items         print i  k  v    Which outputs   0 1 a 1 2 b 2 3 c 3 4 d

User · Answer

enumerate   when working on list actually gives the index and the value of the items inside the list  For example   l    1  2  3  4  5  6  7  8  9  for i  j in enumerate list       print i  j    gives  0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9   where the first column denotes the index of the item and 2nd column denotes the items itself   In a dictionary  enumm    0  1  1  2  2  3  4  4  5  5  6  6  7  7  for i  j in enumerate enumm       print i  j    it gives the output  0 0 1 1 2 2 3 4 4 5 5 6 6 7   where the first column gives the index of the key value pairs and the second column denotes the keys of the dictionary enumm   So if you want the first column to be the keys and second columns as values  better try out dict iteritems   Python 2  or dict items    Python 3   for i  j in enumm items        print i  j    output  0 1 1 2 2 3 4 4 5 5 6 6 7 7   Voila

User · Answer

Python3   One solution   enumm    0  1  1  2  2  3  4  4  5  5  6  6  7  7  for i  k in enumerate enumm       print      d key     d value     format i  k  enumm k        Output  0  enumm key 0  enumm value 1 1  enumm key 1  enumm value 2 2  enumm key 2  enumm value 3 3  enumm key 4  enumm value 4 4  enumm key 5  enumm value 5 5  enumm key 6  enumm value 6 6  enumm key 7  enumm value 7   An another example   d    1     a   1   b    2   c    3        2     a   10   b    20   c    30            for i  k in enumerate d           print      key     value     format i  k  d k       Output          0  key 1  value   a   1   b   2   c   3      1  key 2  value   a   10   b   20   c   30

User · Answer

dict1   a  1   b   banana    To list the dictionary in Python 2 x  for k v in dict1 iteritems            print k v   In Python 3 x use  for k v in dict1 items            print k v    a 1   b banana  Finally  as others have indicated  if you want a running index  you can have that too  for i  in enumerate dict1 items        print i         0    a   1       1    b    banana     But this defeats the purpose of a  dictionary  map  associative array    which is an efficient data structure for telephone-book-style look-up  Dictionary ordering could be incidental to the implementation and should not be relied upon  If you need the order  use   OrderedDict  instead

User · Answer

d    0   zero    0    ZERO   1   one    1    ONE    print  List of enumerated d     list enumerate d items        output   List of enumerated d     0   0   zero      1    0    ZERO      2   1   one      3    1    ONE

[python] enumerate() for dictionary in python

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