How to index into a dictionary

Question

I have a Dictionary below   colors          blue     5        red     6        yellow     8       How do I index the first entry in the dictionary   colors 0  will return a KeyError for obvious reasons

User · Answer

If you need an ordered dictionary  you can use odict

User · Answer

actually I found a novel solution that really helped me out   If you are especially concerned with the index of a certain value in a list or data set  you can just set the value of dictionary to that Index    Just watch   list     a    b    c   dictionary      counter   0 for i in list     dictionary i    counter    counter    1  print dictionary    dictionary     a  0   b  1   c  2    Now through the power of hashmaps you can pull the index your entries in constant time  aka a whole lot faster

User · Answer

Dictionaries are unordered in Python versions up to and including Python 3 6   If you do not care about the order of the entries and want to access the keys or values by index anyway  you can use d keys   i  and d values   i  or d items   i     Note that these methods create a list of all keys  values or items in Python 2 x   So if you need them more then once  store the list in a variable to improve performance    If you do care about the order of the entries  starting with Python 2 7 you can use collections OrderedDict   Or use a list of pairs  l      blue    5      red    6      yellow    8      if you don t need access by key    Why are your numbers strings by the way    In Python 3 7  normal dictionaries are ordered  so you don t need to use OrderedDict anymore  but you still can     it s basically the same type    The CPython implementation of Python 3 6 already included that change  but since it s not part of the language specification  you can t rely on it in Python 3 6

User · Answer

Addressing an element of dictionary is like sitting on donkey and enjoy the ride  As a rule of Python  a DICTIONARY is orderless If there is dic    1   quot a quot   2   quot aa quot   3   quot aaa quot    Now suppose if I go like dic 10     quot b quot   then it will not add like this always dic    1  quot a quot  2  quot aa quot  3  quot aaa quot  10  quot b quot    It may be like dic    1   quot a quot   2   quot aa quot   3   quot aaa quot   10   quot b quot    Or dic    1   quot a quot   2   quot aa quot   10   quot b quot   3   quot aaa quot    Or dic    1   quot a quot   10   quot b quot   2   quot aa quot   3   quot aaa quot    Or any such combination  So a rule of thumb is that a DICTIONARY is orderless

User · Answer

You can t  since dict is unordered  you can use  popitem   to get an arbitrary item  but that will remove it from the dict

User · Answer

oh  that s a tough one  What you have here  basically  is two values for each item  Then you are trying to call them with a number as the key  Unfortunately  one of your values is already set as the key   Try this   colors    1    blue    5    2    red    6    3    yellow    8      Now you can call the keys by number as if they are indexed like a list  You can also reference the color and number by their position within the list   For example   colors 1  0     returns  blue   colors 3  1     returns  8    Of course  you will have to come up with another way of keeping track of what location each color is in  Maybe you can have another dictionary that stores each color s key as it s value                  colors key     blue   1   red   6   yllow   8            Then  you will be able to also look up the colors key if you need to   colors colors key  blue    0  will return  blue   Something like that   And then  while you re at it  you can make a dict with the number values as keys so that you can always use them to look up your colors  you know  if you need                  values    5   1   blue    6   2   red    8   3   yellow              Then   colors colors key values 5  1    0   will return  blue    Or you could use a list of lists   Good luck

User · Answer

If anybody still looking at this question  the currently accepted answer is now outdated   Since Python 3 7  the dictionaries are order-preserving  that is they now behave exactly as collections OrderedDicts used to  Unfortunately  there is still no dedicated method to index into keys     values   of the dictionary  so getting the first key   value in the dictionary can be done as  first key   list colors  0  first val   list colors values    0    or alternatively  this avoids instantiating the keys view into a list    def get first key dictionary       for key in dictionary          return key     raise IndexError  first key   get first key colors  first val   colors first key    If you need an n-th key  then similarly  def get nth key dictionary  n 0       if n  lt  0          n    len dictionary      for i  key in enumerate dictionary keys             if i    n              return key     raise IndexError  dictionary index out of range        CPython 3 6 already included ordered dicts  but this was only an implementation detail  The language specification includes ordered dicts from 3 7 onwards

[python] How to index into a dictionary?

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