Yes, I know its sounds silly. But there is a point...
The R library reticulate allows to use a persistent Python session from a R session. One of its main uses is to allow to use Python code as well as R code in the creation of reports or papers. This is really useful for everyday statistics use...
One can do similar things with Sage and SageTeX, but using R and R objects is a bit awkward. Furthermore, the R tools offer abilities not easily emulated from within Sage. One can create composite documents using R facilities for R code (knitr) and SageTeX (or PythonTeX, better maintained nowadays) for supporting Sage code ; but usng such composite documents is a bit awkward : passing from the source to the compiled document entails :
knitthe R code of the.Rnwfile, getting a.texfile ;\LaTeXthe.texfile at least once ;sage(orpythontex) the resultant file- re-
\LaTeXthe.texfile at least once.
This is a bit hard to automate... The same thing applies with aggravation to Markdown texts : the Sage chunks have to be wrapped in \LaTeX-only chunks, and the sage steps have to be done manually from the command line (or from emacs, which amounts to the same thing).
The availability of a persistent Sage session would solve the problem.
A small trial using Sage's R (launched by sage -R) shows that this is almost possible :
> library(reticulate)
> use_python("/usr/local/sage-8/sage") ## This is the main Sage script file
> repl_python()
Python 2.7.15 (/usr/local/sage-8/sage)
Reticulate 1.10 REPL -- A Python interpreter in R.
>>> 2^3
1
We are in python, no preparsing takes place.
>>> arctan
NameError: name 'arctan' is not defined
arctan is not defined : noting Sage-specific is known.
>>> from sage.all import *
>>> arctan
arctan
The import succeeded.
>>> x
NameError: name 'x' is not defined
But the (default) definition of x as a symbolic variable has not been done.
>>> var("x")
x
>>> x
x
>>> foo=arctan(x).integrate(x)
>>> exit
We are back to R, from which we can access toplevel objects in the Python session :
> py$foo
x*arctan(x) - 1/2*log(x^2 + 1)
> py$latex(py$foo)
x \arctan\left(x\right) - \frac{1}{2} \, \log\left(x^{2} + 1\right)
> py_to_r(py$latex(py$foo))
x \arctan\left(x\right) - \frac{1}{2} \, \log\left(x^{2} + 1\right)
Not a "standard" R characer vector :
> class(py_to_r(py$latex(py$foo)))
[1] "sage.misc.latex.LatexExpr" "python.builtin.str"
[3] "python.builtin.basestring" "python.builtin.object"
But it can be used as such :
> paste("** ",py$latex(py$foo)," **", sep="")
[1] "** x \\arctan\\left(x\\right) - \\frac{1}{2} \\, \\log\\left(x^{2} + 1\\right) **"
Now, it is possible to insert the loading of a Python module before the launch of the Python REPL : From the doc of repl_python :
module: An (optional) Python module to be imported before the REPL is launched.
So the question is : is it possible to write a module correctly importing sage.all AND whose __init__ function would replace Python's REPL by Sage's ?
ISTR that a few years ago, before the introduction of Sage's Jupyter notebook, such tricks were used in Jupyter to start a Sage session (complete with preparser) from an "ordinary" Jupyter notebook. But for the life of me, I haven't been able to retrieve the relevant pages...
Any thoughts ?
