data = [float(datum) for datum in row[:-1]]

This line of code creates a list called "data" by iterating through each element in a list called "row" up until the second-to-last element (i.e. excluding the last element).

For each element in "row", it converts the element to a float using the float() function and adds it to the "data" list.

The resulting "data" list contains all the float values from the "row" list, except for the last element.