[squidbidness]

Here is where "first write good code" applies, at the design level. This function is begging to be two separate, composable functions that each only do one thing.

reverse(addToEach(input_list, 1))

[Kiro]

But what calls "reverse(addToEach(input_list, 1))" if not another function?

[ajuc]

Hopefully a function that can be corectly named.

[Kiro]

What do you think is a better name? reverseListAndAddOneToEachElement is describing the function but I agree it feels ugly.

[IanCal]

For this level of grouping, I'd probably prefer something related to the actual domain.

    def convertDF4ToMX6(data):
        # The MX6 format is read as a stack rather
        # than a queue, and requires data to be 1
        # indexed rather than 0 indexed like DF4
        # link_to_MX6 format spec 1.3.2 (v5)
        # link_to_DF6 format spec 1.2.0 (v1)

Why are we reversing and adding one? What's the reason we need to do that so much that we're combining those two functions into a single call?

This would then mean the calling points might look something like

    mx6_data = convertDF4ToMX6(loadDF4(file))
    return processMX6(mx6_data)

rather than

    mx6_data = reverseAndAddOneToEachElement(loadDF4(file))
    return processMX6(mx6_data)

Rather contrived, I know.