Accessing elements of Python dictionary by index

Question

Consider a dict like  mydict        Apple     American   16    Mexican  10   Chinese  5      Grapes    Arabian   25   Indian   20       How do I access for instance a particular element of this dictionary  for instance  I would like to print the first element after some formatting the first element of Apple which in our case is  American  only   Additional information The above data structure was created by parsing an input file in a python function  Once created however it remains the same for that run   I am using this data structure in my function   So if the file changes  the next time this application is run the contents of the file are different and hence the contents of this data structure will be different but the format would be the same  So you see I in my function I don t know that the first element in Apple is  American  or anything else so I can t directly use  American  as a key

User · Answer

Given that it is a dictionary you access it by using the keys. Getting the dictionary stored under "Apple", do the following:

>>> mydict["Apple"]
{'American': '16', 'Mexican': 10, 'Chinese': 5}

And getting how many of them are American (16), do like this:

>>> mydict["Apple"]["American"]
'16'

User · Answer

Simple Example to understand how to access elements in the dictionary - Create a Dictionary d     dog     bark    cat     meow     print d get  cat    print d get  lion    print d get  lion    Not in the dictionary    print d get  lion    NA    print d get  dog    NA     Explore more about Python Dictionaries and learn interactively here

User · Answer

You can use mydict  Apple   keys   0  in order to get the first key in the Apple dictionary  but there s no guarantee that it will be American  The order of keys in a dictionary can change depending on the contents of the dictionary and the order the keys were added

User · Answer

If the questions is  if I know that I have a dict of dicts that contains  Apple  as a fruit and  American  as a type of apple  I would use   myDict     Apple     American   16    Mexican  10   Chinese  5              Grapes    Arabian   25   Indian   20       print myDict  Apple    American     as others suggested  If instead the questions is  you don t know whether  Apple  as a fruit and  American  as a type of  Apple  exist when you read an arbitrary file into your dict of dict data structure  you could do something like   print  ftype  American   for f ftype in myDict iteritems   if f     Apple  and  American  in ftype    or better yet so you don t unnecessarily iterate over the entire dict of dicts if you know that only Apple has the type American   if  Apple  in myDict      if  American  in myDict  Apple            print myDict  Apple    American     In all of these cases it doesn t matter what order the dictionaries actually store the entries  If you are really concerned about the order  then you might consider using an OrderedDict   http   docs python org dev library collections html collections OrderedDict

User · Answer

With the following small function  digging into a tree-shaped dictionary becomes quite easy   def dig tree  path       for key in path split               if isinstance tree  dict  and tree get key               tree   tree key          else              return None     return tree   Now  dig mydict   Apple Mexican   returns 10  while dig mydict   Grape   yields the subtree   Arabian   25   Indian   20    If a key is not contained in the dictionary  dig returns None   Note that you can easily change  or even parameterize  the separator char from     to          etc

User · Answer

I know this is 8 years old  but no one seems to have actually read and answered the question   You can call  values   on a dict to get a list of the inner dicts and thus access them by index     gt  gt  gt  mydict           Apple     American   16    Mexican  10   Chinese  5         Grapes    Arabian   25   Indian   20       gt  gt  gt mylist   list mydict values     gt  gt  gt mylist 0    American   16    Mexican  10   Chinese  5    gt  gt  gt mylist 1    Arabian   25   Indian   20     gt  gt  gt myInnerList1   list mylist 0  values     gt  gt  gt myInnerList1   16   10  5   gt  gt  gt myInnerList2   list mylist 1  values     gt  gt  gt myInnerList2   25    20

User · Answer

You can t rely on order of dictionaries  but you may try this  mydict  Apple   items   0  0   If you want the order to be preserved you may want to use this  http   www python org dev peps pep-0372  ordered-dict-api

User · Answer

mydict      Apple     American   16    Mexican  10   Chinese  5    Grapes    Arabian   25   Indian   20      for n in mydict      print mydict n

User · Answer

As I noticed your description  you just know that your parser will give you a dictionary that its values are dictionary too like this  sampleDict                    quot key1 quot     quot key10 quot    quot value10 quot    quot key11 quot    quot value11 quot                   quot key2 quot     quot key20 quot    quot value20 quot    quot key21 quot    quot value21 quot                    So you have to iterate over your parent dictionary  If you want to print out or access all first dictionary keys in sampleDict values   list  you may use something like this  for key  value in sampleDict items        print value keys   0   If you want to just access first key of the first item in sampleDict values    this may be useful  print sampleDict values   0  keys   0   If you use the example you gave in the question  I mean  sampleDict                    Apple     American   16    Mexican  10   Chinese  5                  Grapes    Arabian   25   Indian   20                    The output for the first code is  American Indian  And the output for the second code is  American  EDIT 1  Above code examples does not work for version 3 and above of python  since from version 3  python changed the type of output of methods keys and values from list to dict values  Type dict values is not accepting indexing  but it is iterable  So you need to change above codes as below  First One  for key  value in sampleDict items        print list value keys    0    Second One  print list list sampleDict values    0  keys    0

User · Answer

As a bonus  I d like to offer kind of a different solution to your issue  You seem to be dealing with nested dictionaries  which is usually tedious  especially when you have to check for existence of an inner key   There are some interesting libraries regarding this on pypi  here is a quick search for you   In your specific case  dict digger seems suited    gt  gt  gt  import dict digger  gt  gt  gt  d        Apple     American   16    Mexican  10   Chinese  5      Grapes    Arabian   25   Indian   20        gt  gt  gt  print dict digger dig d   Apple   American    16  gt  gt  gt  print dict digger dig d   Grapes   American    None

User · Answer

Few people appear  despite the many answers to this question  to have pointed out that dictionaries are un-ordered mappings  and so  until the blessing of insertion order with Python 3 7  the idea of the  first  entry in a dictionary literally made no sense  And even an OrderedDict can only be accessed by numerical index using such uglinesses as mydict mydict keys   0    Python 2 only  since in Python 3 keys   is a non-subscriptable iterator    From 3 7 onwards and in practice in 3 6 as well - the  new behaviour was introduced then  but not included as part of the language specification until 3 7 - iteration over the keys  values or items of a dict  and  I believe  a set also  will yield the least-recently inserted objects first  There is still no simple way to access them by numerical index of insertion   As to the question of selecting and  formatting  items  if you know the key you want to retrieve in the dictionary you would normally use the key as a subscript to retrieve it  my var   mydict  Apple      If you really do want to be able to index the items by entry number  ignoring the fact that a particular entry s number will change as insertions are made  then the appropriate structure would probably be a list of two-element tuples  Instead of  mydict        Apple     American   16    Mexican  10   Chinese  5      Grapes    Arabian   25   Indian   20       you might use   mylist           Apple     American   16    Mexican  10   Chinese  5          Grapes     Arabian    25    Indian    20       Under this regime the first entry is mylist 0  in classic list-endexed form  and its value is   Apple     American   16    Mexican  10   Chinese  5    You could iterate over the whole list as follows   for  key  value  in mylist     unpacks to avoid tuple indexing     if key     Apple           if  American  in value              print value  American      but if you know you are looking for the key  Apple   why wouldn t you just use a dict instead   You could introduce an additional level of indirection by cacheing the list of keys  but the complexities of keeping two data structures in synchronisation would inevitably add to the complexity of your code

[python] Accessing elements of Python dictionary by index

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