Last Key in Python Dictionary

Question

I am having difficulty figuring out what the syntax would be for the last key in a Python dictionary  I know that for a Python list  one may say this to denote the last   list -1    I also know that one can get a list of the keys of a dictionary as follows   dict keys     However  when I attempt to use the logical following code  it doesnt work   dict keys -1    It says that keys cant take any arguments and 1 is given  If keys cant take args  then how can I denote that I want the last key in the list   XXXXX I am operating under the assumption that Python dictionaries are ordered in the order in which items are added to the dictionary with most recent item last  For this reason  I would like to access the last key in the dictionary XXXXX  I am now told that the dictionary keys are not in order based on when they were added  How then would I be able to choose the most recently added key

User · Answer

It doesn t make sense to ask for the  last  key in a dictionary  because dictionary keys are unordered  You can get the list of keys and get the last one if you like  but that s not in any sense the  last key in a dictionary

User · Answer

If insertion order matters  take a look at collections OrderedDict   An OrderedDict is a dict that remembers the order that keys were first inserted  If a new entry overwrites an existing entry  the original insertion position is left unchanged  Deleting an entry and reinserting it will move it to the end    In  1   from collections import OrderedDict  In  2   od   OrderedDict zip  bar   foo     In  3   od Out 3   OrderedDict    b    f      a    o      r    o      In  4   od keys   -1  Out 4    r   In  5   od popitem     also removes the last item Out 5     r    o    Update  An OrderedDict is no longer necessary as dictionary keys are officially ordered in insertion order as of Python 3 7  unofficially in 3 6   For these recent Python versions  you can instead just use list my dict  -1  or list my dict keys    -1

User · Answer

There s a definite need to get the last element of a dictionary  for example to confirm whether the latest element has been appended to the dictionary object or not   We need to convert the dictionary keys to a list object  and use an index of -1 to print out the last element   mydict     John   apple   Mat   orange   Jane   guava   Kim   apple   Kate    grapes    mydict keys        output  dict keys   John    Mat    Jane    Kim    Kate      list mydict keys         output    John    Mat    Jane    Kim    Kate     list mydict keys    -1       output   Kate

User · Answer

yes there is   len data -1   For the first element it  s   0

User · Answer

Since python 3 7 dict always ordered insert order   since python 3 8 keys    values   and items   of dict returns  view that can be reversed  to get last key  next reversed my dict keys        the same apply for values   and items   PS  to get first key use  next iter my dict keys

User · Answer

sorted dict keys    -1    Otherwise  the keys is just an unordered list  and the  last one  is meaningless  and even can be different on various python versions    Maybe you want to look into OrderedDict

User · Answer

In python 3 6 I got the value of last key from the following code  list dict keys    -1

User · Answer

You can do a function like this   def getLastItem dictionary       last keyval   dictionary popitem       dictionary update  last keyval 0  last keyval 1        return  last keyval 0  last keyval 1     This not change the original dictionary  This happen because the popitem   function returns a tuple and we can utilize this for us favor

User · Answer

It seems like you want to do that  dict keys   -1   dict keys   returns a list of your dictionary s keys  Once you got the list  the -1 index allows you getting the last element of a list  Since a dictionary is unordered   it s doesn t make sense to get the last key of your dictionary  Perhaps you want to sort them before  It would look like that  sorted dict keys    -1   Note  In Python 3  the code is list dict  -1    Update  This is no longer the case  Dictionary keys are officially ordered as of Python 3 7  and unofficially in 3 6

User · Answer

There are absolutely very good reason to want the last key of an OrderedDict   I use an ordered dict to list my users when I edit them  I am using AJAX calls to update user permissions and to add new users  Since the AJAX fires when a permission is checked  I want my new user to stay in the same position in the displayed list  last  for convenience until I reload the page  Each time the script runs  it re-orders the user dictionary   That s all good  why need the last entry   So that when I m writing unit tests for my software  I would like to confirm that the user remains in the last position until the page is reloaded   dict keys   -1    Performs this function perfectly  Python 2 7

[python] Last Key in Python Dictionary

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