[Tutor] How to print corresponding keys in Dictionary

[Dave Angel]

On 10/24/2011 09:10 AM, Praveen Singh wrote:
> In Dictionary-
> How to print corresponding keys if the values of dictionary is given??
>
> -d={'a':1,'b':2,'c':3}
> -i can print the corresponding values by using get() method-
> - d.get('a')
> -1
>
> What if i have to print reverse???
>
>
A dictionary can be viewed as a mapping between keys and values, where 
you supply a key, and the dictionary quickly finds the corresponding 
value.  To do the reverse, you have to construct the code yourself and 
it will be much smaller, if there are many items.

For example (untested):

d = {"a", 1, "b":2, "c":3, "d":2}

def getkey(dictionary, value):
      for key, val in dictionary.items():
            if val == value:
                   return key


Note that if there are multiple keys with the same value, my function 
would get only the first.  It wouldn't be hard to modify the function to 
return a list of matching keys.

-- 

DaveA