One reason is that lots of operations automatically join on index (instead of, say, using rows’ integer indices) which makes them more convenient than manually doing the join yourself every time. You only need to set the indices correctly one and then things just work.
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One reason is that lots of operations automatically join on index (instead of, say, using rows’ integer indices) which makes them more convenient than manually doing the join yourself every time. You only need to set the indices correctly one and then things just work.
This is the biggest thing. Indexes are like an extension of array broadcasting to relational data.
Not least in that both broadcasting and pandas indicies seem surprising and magical if one doesn’t understand the details.