JuliaCall: is it possible to pass objects from Python to Julia Main?

General Usage
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1

Using JuliaCall, is it possible to pass objects from Python to Julia so that I can then use them in evaluated Julia code ?

E.g.:

>>> from juliacall import Main as jl
>>> xpy = [1,2,3]
>>> jl.xj = xpy # AttributeError: 'ModuleValue' object has no attribute 'xj'
>>> s = jl.seval("sum(xj)") # this is where I want to arrive

Of course, I am aware I can simply do in this case:

>>> jl.sum(xpy)

but I wonder if I can explicitly transfer (possibly without manually using convert) objects from Python to Julia.

2

It’s admittedly not clear (I’ve now fixed this) but if you read down the full error stack the underlying error is:

AttributeError: Julia: cannot assign variables in other modules

which means that you can only assign a variable to a Julia module from code executing inside the module - this is a general Julia restriction.

If you really want you can write a function which uses @eval to do it:

>>> jlstore = jl.seval("(k, v) -> (@eval $(Symbol(k)) = $v; return)")
>>> jlstore("foo", [1,2,3])
>>> jl.foo
[1, 2, 3]
1 Like
3

Yes, it works:

>>> from juliacall import Main as jl
>>> xpy = [1,2,3]
>>> jlstore = jl.seval("(k, v) -> (@eval $(Symbol(k)) = $v; return)")
>>> jlstore("xj", xpy)
>>> s = jl.seval("sum(xj)")
>>> s
6

I think it would be useful to have this function in JuliaCall. Both PyJulia and R JuliaCall have something similar:

>>> jl = julia.Julia(compiled_modules=False)
>>> import julia
>>> from julia import Main
>>> xpy = [1,2,3]
>>> Main.xj = xpy
>>> jl.eval("sum(xj)")
6

> library(JuliaCall)
> xr = c(1,2,3)
> julia_assign("xj",xr)
> julia_eval("sum(xj)")
[1] 6
>