Python check object keys exists

keysExist.py

# Search an object heirarchy for the presence of the given keys
def keyExists(obj, keys):
    first, rest = keys[0], keys[1:]
    if first in obj or len(obj) > int(first):
        if len(rest) == 0:
            return True
        return keyExists(obj[first], rest)
    return False


# Example
onion = {
    "layers" : [
        {
            "skin" : {
                "colour" : "brown",
                "depth" : 1
            }    
        },
        {
            "skin" : "green"
        }
    ]
}

if keyExists(onion, ["layers",0, "skin", "colour"]):
    print "the onion has {} skin!".format(onion["layers"][0]["skin"]["colour"])

Probably a one line lambda expression that does the same, but this is easier to understand