Merge two dict in separate list by id
You are saying 


  I want to merge the dictionary present


but what makes your task a bit difficult is that you are not handling dictonnaries but lists. Among other things, if you keep that idea that way, you'll have to iterate over n*m pairs (ta, tb) (where n and m are respective size of a and b).

A probably better idea would be to reorganise data in a and b to have them as an actual dict mapping id to some additional information. Then, merging will go through maximum n + m elements.