cities = {'CA': 'San Francisco', 'MI': 'Detroit',
                    'FL': 'Jacksonville'}

cities['NY'] = 'New York'
cities['OR'] = 'Portland'

def find_city(themap, state):
    if state in themap:
        return themap[state]
    else:
        return "Not found."

# ok pay attention!
cities['_find'] = find_city

while True:
    print ("State? (ENTER to quit)"),
    state = input("> ")

    if not state: break

    # this line is the most important ever! Study!
    city_found = cities['_find'](cities, state)
    print (city_found)

cities[‘_find’] = find_city這里的cities[‘_find’]（是創(chuàng)建的字典中的一個元素）被賦值成find__city函數(shù)，也可以理解為cities[‘_find’]是一個函數(shù)變量。