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()