I am making relationships from a dictionary, but can someone help me fix one output I can't figure out?

Question

What I am trying to do is make an ancestor dictionary of sorts, which I have succeeded in doing. My only problem is that when a relationship doesn't exist, my program should output "The relationship isn't in the dictionary." I know how to do that when the key is not in the dictionary, but how do I do that with the value?

Here is my code:

relationships = {"Jalen": "Joseph", "Arthur": "Joseph", "Mike": "Joseph", "Chris": "Joseph", "Joseph": "Thomas", "Jesse": "Marcus", "Marcus": "Gerhard", "Gerhard": "Allan", "Allan": "Thomas", "James": "Gerhard"}
print relationships

def menu():
    print ("To find a father, press 1.")
    print ("To find a grandfather, press 2.")
    print ("To find a great-grandfather, press 3.")
    print ("To exit the program, press 0,")
    while True:
        choice = input("Enter your choice of action: ")
        if (choice >= 0) and (choice <= 3):
            return choice
        else:
            print("Invalid option. Enter an integer from 0 to 3")

def father(n):
    if relationships.has_key(n):
        return relationships[n]

def grandfather(n):
    if relationships.has_key(n):
        father = relationships[n]
        if relationships.has_key(father):
            return relationships[father]

def greatgrandfather(n):
    if relationships.has_key(n):
        father = relationships[n]
        if relationships.has_key(father):
            grandfather = relationships[father]
            if relationships.has_key(grandfather):
                return relationships[grandfather]

def main ():
    while True:
        choice = menu()
        if choice == 0:
            break
        else:
            name = raw_input("Please enter the name of the person for whom you seek an ancestory: ")
            if relationships[name]:
                if choice == 1:
                    print "The father of ", name, " is ", father(name), "."
                elif choice == 2:
                    print "The grandfather of ", name, " is ", grandfather(name), "."
                else:
                    print "The great-grandfather of ", name, " is ", greatgrandfather(name), "."
            else:
                print "This relationship is not in our records."


main()

How would I check to see if the relationship exists in the values or not? Python language.

Answer 1

The in keyword is used to check if a value or key is in a dictionary. So, all you have to do to check if a key exists in a dictionary is:

if record not in relationships:
    print "This relationship is not in our records.

Answer 2

if aRelationship in relationships.values():
    #aRelationship in relationships.values()
else:
    #aRelationship  not in relationships.values()