# 1

importjson

# 2

dict_a={}

dict_b=dict()

# 3

dict_a={"a1":"b1","a2":"b2","a3":"b3"}

# 4

ks=dict_a.keys()

print(type(ks))

# 5

vs=dict_a.values()

print(type(vs))

# 6

print(dict_a.items())

# 7

dict_a["a1"] ="b3"

dict_a["a3"] ="b1"

# 8

print(dict_a)

# 9

dict_a.pop("a1")

# 10

print(dict_a)

# 11

dict_b.update(dict_a)

# 12

print(dict_b)

# 13

a1=dict_b.get('a1')

print(a1)

# 14

dict_b["a1"] =a1

# 15

dict_b["a4"] ='null'

# 16

print(dict_b)

print(type(dict_b))

# 17

json_c=json.dumps(dict_b)

# 18  None --> null None为python特有的数据类型

print(json_c)

print(type(json_c))

# 19

dict_c=json.loads(json_c)

print(dict_b)