PyQtGraph. What is the best way to store a large number of chart elements?

Question

PyQt

The data comes to the program one float and one datetime. Somewhere every 4 seconds. And this is somewhere around 20,000 per day and not one day.
float is written to the graph curve in natural order of arrival. datetime should appear when hovering over the corresponding float.
All this goodness will have to be analyzed by the user by rereading the data of the range of interest and drawing a beautiful result of these calculations next to it on the graph. All this without interruption from the constant replenishment of new data.
As you know, lists are good for growing or changing, but bad for index access, and arrays are the other way around.
What should I do in my case?
PS: If anyone is interested, then I take data from the mt4 forex terminal and put it into python to do everything that is not available for mt4.