The Python module JuliaCall
Installation
It's as simple as
pip install juliacall
Developers may wish to clone the repo (https://github.com/JuliaPy/PythonCall.jl) directly and pip install the module in editable mode. You should add "dev":true, "path":"../.."
to pysrc/juliacall/juliapkg.json
to ensure you use the development version of PythonCall in conjunction with JuliaCall.
Getting started
For interactive or scripting use, the simplest way to get started is:
from juliacall import Main as jl
This loads a single variable jl
which represents the Main
module in Julia, from which all of Julia's functionality is available:
jl.println("Hello from Julia!")
# Hello from Julia!
x = jl.rand(range(10), 3, 5)
x._jl_display()
# 3×5 Matrix{Int64}:
# 8 1 7 0 6
# 9 2 1 4 0
# 1 8 5 4 0
import numpy
numpy.sum(x, axis=0)
# array([18, 11, 13, 8, 6], dtype=int64)
In this example:
- We called the
jl.println
function to print a message. - We called the
jl.rand
function to generate an array of random integers. Note that the first argument isrange(10)
which is converted to0:9
in Julia. - We called its special
_jl_display()
to show it using Julia's display mechanism. - We called the
numpy.sum
function to sum each column ofx
. This automatically convertedx
to a NumPy array. (We could have donejl.sum(x, dims=1)
too.)
If you are writing a package which uses Julia, then to avoid polluting the global Main
namespace you instead should start with:
import juliacall
jl = juliacall.newmodule("SomeName")
Julia modules have a special method seval
which will evaluate a given piece of code given as a string in the module. This is most frequently used to import modules:
from array import array
jl.seval("using Statistics")
x = array('i', [1, 2, 3])
jl.mean(x)
# 2.0
y = array('i', [2,4,8])
jl.cor(x, y)
# 0.9819805060619657
What to read next:
- The main functionality of this package is in
AnyValue
objects, which represent Julia objects, documented here. - If you need to install Julia packages, read here.
- When you call a Julia function, such as
jl.rand(...)
in the above example, its arguments are converted to Julia according to this table and its return value is converted to Python according to this table.
Managing Julia dependencies
JuliaCall manages its Julia dependencies using JuliaPkg.
It will automatically download a suitable version of Julia if required.
A Julia environment is also created, activated and populated with any required packages. If you are in a virtual or Conda environment, the environment is put there. Otherwise a global environment is used at ~/.julia/environments/pyjuliapkg
.
If your project requires any Julia packages, or a particular version of Julia itself, then create a file called juliapkg.json
in your package. For example: Here is an example:
{
"julia": "1.5",
"packages": {
"Example": {
"uuid": "7876af07-990d-54b4-ab0e-23690620f79a",
"version": "0.5, 0.6"
}
}
}
Alternatively you can use add
, rm
, etc. from JuliaPkg to edit this file.
See JuliaPkg for more details.
Configuration
Some features of the Julia process, such as the optimization level or number of threads, may be configured in two ways:
- As an
-X
argument to Python, such as-X juliacall-optlevel=3
; or - As an environment variable, such as
PYTHON_JULIACALL_OPTLEVEL=3
.
-X option | Environment Variable | Description |
---|---|---|
-X juliacall-home=<dir> | PYTHON_JULIACALL_BINDIR=<dir> | The directory containing the julia executable. |
-X juliacall-check-bounds=<yes|no|auto> | PYTHON_JULIACALL_CHECK_BOUNDS=<yes|no|auto> | Enable or disable bounds checking. |
-X juliacall-compile=<yes|no|all|min> | PYTHON_JULIACALL_COMPILE=<yes|no|all|min> | Enable or disable JIT compilation. |
-X juliacall-compiled-modules=<yes|no> | PYTHON_JULIACALL_COMPILED_MODULES=<yes|no> | Enable or disable incrementally compiling modules. |
-X juliacall-depwarn=<yes|no|error> | PYTHON_JULIACALL_DEPWARN=<yes|no|error> | Enable or disable deprecation warnings. |
-X juliacall-handle-signals=<yes|no> | PYTHON_JULIACALL_HANDLE_SIGNALS=<yes|no> | Enable or disable Julia signal handling. |
-X juliacall-inline=<yes|no> | PYTHON_JULIACALL_INLINE=<yes|no> | Enable or disable inlining. |
-X juliacall-min-optlevel=<0|1|2|3> | PYTHON_JULIACALL_MIN_OPTLEVEL=<0|1|2|3> | Optimization level. |
-X juliacall-optimize=<0|1|2|3> | PYTHON_JULIACALL_OPTIMIZE=<0|1|2|3> | Minimum optimization level. |
-X juliacall-procs=<N|auto> | PYTHON_JULIACALL_PROCS=<N|auto> | Launch N local worker process. |
-X juliacall-startup-file=<yes|no> | PYTHON_JULIACALL_STARTUP_FILE=<yes|no> | Enable or disable your startup.jl file. |
-X juliacall-sysimage=<file> | PYTHON_JULIACALL_SYSIMAGE=<file> | Use the given system image. |
-X juliacall-threads=<N|auto> | PYTHON_JULIACALL_THREADS=<N|auto> | Launch N threads. |
-X juliacall-warn-overwrite=<yes|no> | PYTHON_JULIACALL_WARN_OVERWRITE=<yes|no> | Enable or disable method overwrite warnings. |
-X juliacall-autoload-ipython-extension=<yes|no> | PYTHON_JULIACALL_AUTOLOAD_IPYTHON_EXTENSION=<yes|no> | Enable or disable IPython extension autoloading. |