If there are any geeks out there like me, I’ve just written my first Python script and posting here as it’s a little tool that will let you enter your FTP and give you either time, NP or TSS you need given the other two numbers.
So, for example you can say I want to ride at 300w normalised power, for 45 minutes and it will tell you what TSS score you will get. Or you could say if I want 45 TSS and I’ve got 20 minutes to get it, what NP do I need.
Only sharing here as I’m totally brand new to Python and I welcome any feedback from the brains in the group. But also I know for some of you who do your own planning it “may” be of use 
I do also have my original Excel version that took me about a tenth of the time to build lol. I can’t upload the files, but if anyone wants them just shout. Below is a screenshot of how iot looks if you run it in a terminal:
(NB: This isn’t intended to start a debate about the merits of a TSS/FTP based system 
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