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Given a dictionary d and a key k and value v, if you have v and you want to find k? It’s a reverse look up. This week, we wrote a function reverse_lookupdef reverse_lookup(d, v):for k in d:
if d[k] == v:
return k
raise ValueError(‘value does not appear in the dictionary’)
Task:
Modify reverse_lookup and implement a function better_reverse_lookup so that it builds and returns a list of all keys that map to v, or an empty list if there are none.
>>> h = histogram(‘apple’)
>>> #histogram is a function that creates a dictionary mapping of letter and count of how many times it appearances in a string.
>>> #for example, histogram(‘apple’) returns a dictionary of {‘a’:1, ‘e’:1, ‘p’:2, ‘l’:1}. You don’t need to implement the histogram function.
>>> lst = better_reverse_lookup(h, 1) # will return all letters that mapped to count 1 in the dictionary
>>> lst
[‘a’, ‘l’, ‘e’]
>>> lst = better_reverse_lookup(h, 3)
>>> lst
[]
Hint: List method append adds a new element to the end of a list:
>>> t = [‘a’, ‘b’, ‘c’]
>>> t.append(‘d’)
>>> t
[‘a’, ‘b’, ‘c’, ‘d’]