Accessing items in lists within dictionary python

Question

I have a dictionary that has keys associated with lists.

mydict = {\'fruits\': [\'banana\', \'apple\', \'orange\'],
         \'vegetables\': [\'pepper\', \'carr         


        

Answer 1

mydict = {'fruits': ['banana', 'apple', 'orange'],
     'vegetables': ['pepper', 'carrot'], 
     'cheese': ['swiss', 'cheddar', 'brie']}

item = "cheddar"

for key, values in mydict.iteritems():
    if item in values:
        print key

If you are going to do a lot of this kind of searching, I think you can create a reverse index for the original mydict to speed up querying:

reverse_index = {}

for k, values in mydict.iteritems():
     for v in values:
         reverse_index[v] = k

print reverse_index.get("cheddar")
print reverse_index.get("banana")

This way you don't have to traverse the values list every time to find an item.