# Selecting specific values in Sage

I have the following solution:

solve(...)=[[xa1 == R*a/((a + b)*p1), xa2 == R*b/(a + b), l1 == (a + b)*(R*b/(a + b))^b*(R*a/((a + b)*p1))^a/R]]


Im aware I can get the whole set of solutions back with the use of

solve(...)[0]
[xa1 == R*a/((a + b)*p1), xa2 == R*b/(a + b), l1 == (a + b)*(R*b/(a + b))^b*(R*a/((a + b)*p1))^a/R]


Im only interested in getting back xa1. Is there a way to do that?

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A solution I found to this problem is that you need to do as follows:

 solution1=solve(...)[0]
solution1[0]

xa1 == R*a/((a + b)*p1), xa2 == R*b/(a + b)

more

1

solution1(0][0] i more streamlined. And faster.

You should peruse a Python tutorial ; Python lends itself to a lot of useful idioms,which may be time consuming to discover by yourself.

I cannot recommend enough this marvelous book on Sage, even if it's a bit outdated (reporting on a Python 2-based version of Sage, whereas Sage is Python 3-based : version 9.1 and later support only Python 3).

( 2020-07-16 12:32:12 +0100 )edit

@EmmanuelCharpentier Thanks for the tip!

( 2020-07-16 16:30:02 +0100 )edit