How would I display a seconds value as SI years?

Astropy
1

val = 100000000 * u.s
print(val.to(units.yr) ) # Year, non-SI
print(val.to(units.yr).si) # Returns seconds!

I’m sure there’s something obvious I’m missing here…

2

As far as I know, there is no such thing as an “SI year”. A year is a non-SI unit, and – unlike the non-SI time units of minute, hour, or day – it’s not even one of the non-SI units that are officially accepted for use with SI (see Non-SI units mentioned in the SI - Wikipedia, or Section 4 of the SI Brochure). Can you elaborate on what you expected that call to return?

1 Like
3

So my understanding of ‘SI’ (Scientific Notation?) is that you get a number like this:
3 * 10^6 seconds.
And if I do
val.to(units.yr).si
I get something like that in seconds:
x * 10^y seconds
But what I want to display is the number of years in the same format:
x * 10^y years

So it’s easy to convert to years, but I seem to get the implicit conversion back to seconds.

4

It seems that:
print(“{:e}”.format(val.to(units.yr)))
gives me what I was after.

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5

SI = Système international, this describes the set of units (see link above); it has nothing to do with the formatting of the numbers.

6

Yeah, I thought it meant ‘scientific notation’, hence the confusion!