ARDUINO YUN REV 2 - Speed writing is slow (Bridge)

Thank you for your time

At first, I have collect samples in arduino sketch (300~400 samples are maximum, because memory are really limited) and write in SD card with FileIO, but it is equivalent of 3-4sec of measure and 10sec of writing, and it isnt enough (I think I can deal with it, but more is better).
Here, it process a lot in arduino sketch

But I don't really get it, for one of your project, when you read and total 1000 samples, then Linux divided by the number of samples, it seem each value is averaged ?

BTW, do you have a guide for beginner like me, to run python in Arduino Yun ?