python - Most efficient method to get key for a value in a dict

Question

I have a dictionary of objects:

dic = {'k1':obj1, 'k2':obj2, 'k3':obj3, ...}

class MyObject:
    def __init__(self,x,y):
        self.x=x
        self.y=y

I wonder how I can have the best implementation for finding the key that corresponds to a value. Something equivalent to:

def find_key(dic, val):
    for k,v in dic.items():
        if v==val:
            return k
    return None

NB: Sorry if this is obvious, I am a newbie in Python :-)

Answer 1

Ignoring the possibility that samb8s raises, that multiple keys exist for a single value, you can easily reverse the dictionary like this:

reverse_dic = dict((v, k) for k, v in dic.items())