Python get key of index in dictionary

Question

Possible Duplicate    Inverse dictionary lookup - Python   reverse mapping of dictionary with Python       How do i get key of index in dictionary   For example like   i     a   0   b   1   c   2    so if i want to get key of i 0   it will return  a

User · Answer

Python dictionaries have a key and a value, what you are asking for is what key(s) point to a given value.

You can only do this in a loop:

[k for (k, v) in i.iteritems() if v == 0]

Note that there can be more than one key per value in a dict; {'a': 0, 'b': 0} is perfectly legal.

If you want ordering you either need to use a list or a OrderedDict instance instead:

items = ['a', 'b', 'c']
items.index('a') # gives 0
items[0]         # gives 'a'

User · Answer

You could do something like this   i   foo   bar    baz   huh    keys i keys     in python 3  you ll need  list i keys     values i values   print keys values index  bar       foo    However  any time you change your dictionary  you ll need to update your keys values because dictionaries are not ordered in versions of Python prior to 3 7  In these versions  any time you insert a new key value pair  the order you thought you had goes away and is replaced by a new  more or less random  order   Therefore  asking for the index in a dictionary doesn t make sense   As of Python 3 6  for the CPython implementation of Python  dictionaries remember the order of items inserted  As of Python 3 7  dictionaries are ordered by order of insertion   Also note that what you re asking is probably not what you actually want   There is no guarantee that the inverse mapping in a dictionary is unique   In other words  you could have the following dictionary   d   i  1   j  1    In that case  it is impossible to know whether you want i or j and in fact no answer here will be able to tell you which   i  or  j   will be picked  again  because dictionaries are unordered    What do you want to happen in that situation   You could get a list of acceptable keys     but I m guessing your fundamental understanding of dictionaries isn t quite right

User · Answer

By definition dictionaries are unordered  and therefore cannot be indexed  For that kind of functionality use an ordered dictionary  Python Ordered Dictionary

[python] Python: get key of index in dictionary

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