Creating multidictionaries in one

[somebrick]

Hey guys! So basically, how would I save a prior of a dictionary before its values are changed. And also I want the format to be like this;

{'A':None,{'R1': [5,4,2,6,4],'R2':[6,5,4,7,4],'R3':[6,2,4,7,3]

I would like to have the user input the values for r1,r2,r3 and if there is no value make it none. How would i do that?