I'm sure this question must have already been answered somewhere but I couldn't find an answer that suits my case.
I have 2 pandas DataFrames
a = pd.DataFrame({'A1':[1,2,3], 'A2':[2,4,6]}, index=['a','b','c'])
b = pd.DataFrame({'A1':[3,5,6], 'A2':[3,6,9]}, index=['a','c','d'])
我想合并它们以获得类似的结果
result = pd.DataFrame({
'A1' : [3,2,5,6],
'A2' : [3,4,6,9]
}, index=['a','b','c','d'])
Basically, I want a new df with the union of both indexes. Where indexes match, the value in each column should be updated with the one from the second df (in this case b). Where there is no match the value is taken from the starting df (in this case a).
I tried with merge(), join() and concat() but I could not manage to obtain this result.