Which lib can diff two dict tree?

[esbatmop at gmail.com]

Q1：
dict a：{'a1': 'b1', 'a2': {'b2': 'c2'}, 'a3': 'b3'}
dict b：{'a1': 'b1', 'a2': {'b2': 'c3'}}
which lib can diff two dict tree？
like：
print struct_diff(a，b)
>>tree 'a3'
print value_diff(a,b)
>>c3

Q2
How can I diff two json file?How can I get struct_diff and value_diff?

Q3
How can I diff two xml file? How can I get struct_diff and value_diff?