> > In my opinion, when you did `df[20:50,:]`, you constructed a new > DataFrame, which had no longer anything to do with the original `df`. So > you cannot expect it to know the original position in `df`. And when you > print it, the row number (instead of index) is generated on the fly, just > let you know which value is at which line of the output. > > I think what needed here is just a formatted `print()` for DataFrame, > which can toggle the row number index. >
When I do `df[20:50,:]`, the result is a subset of the original DataFrame `df`, so I should expect to keep track of the index in `df`. It doesn't take much to see why that is useful (an index often refers to a person, geographical entity, discrete period of time, etc).
