def add(a, b):
    return a + b


def sub(a, b):
    return a - b


def demo_dict():
    dicta={4:16,1:1,2:4,3:9}
   # dicta = {4: 16, 1: 1, 2: 4, 3: 9}
    print (1,dicta)
    print (2,dicta.keys(), dicta.values())
    print (3, 1 in dicta, '3' in dicta)
    for key, value in dicta.items():
        print (key, value)
    dictb = {'+': add, '-': sub}
    print (4, dictb['+'](1, 2))
    print (5, dictb.get('-')(15, 3))
    dictb['*'] = 'x'
    print (dictb)
    dicta.pop(4)
    print (6, dicta)
    del dicta[1]
    print (7,dicta)


if __name__ == '__main__':
    demo_dict()