GraalPython support in JBang

[wfouche]

Starting a discussion exploring support for GraalPython in JBang. Is it feasible, how would it work, what are the benefits and limitations?

GraalPython in located in Maven Central at:

<dependency>
    <groupId>org.graalvm.polyglot</groupId>
    <artifactId>python</artifactId>
    <version>24.1.2</version>
</dependency>

GraalPython is a Python 3.11 compliant runtime on top of the GraalVM (JVM):

• https://github.com/oracle/graalpython/releases
• https://www.graalvm.org/python/
• https://www.graalvm.org/latest/reference-manual/python/standalone-applications/
• https://www.graalvm.org/latest/reference-manual/python/Modern-Python-on-JVM/#migrating-jython-scripts

[wfouche]

Moving from Jython to GraalPython:

• https://github.com/graalvm/graal-languages-demos/tree/main/graalpy/graalpy-jython-guide

GraalPython with JBang integration demo:

• https://github.com/graalvm/graal-languages-demos/tree/main/graalpy/graalpy-jbang-qrcode/

[wfouche]

// Install the Graal VM
$ sdk install java 23.0.2-graal

// Run the Graal Python code
$ time jbang run qrcode.java "Hello from GraalPy!"

[jbang] Resolving dependencies...
[jbang]    org.graalvm.python:python-language:24.1.2
[jbang]    org.graalvm.python:python-launcher:24.1.2
[jbang]    org.graalvm.python:python-resources:24.1.2
[jbang]    org.graalvm.python:python-embedding:24.1.2
[jbang]    org.graalvm.python:python-embedding-tools:24.1.2
[jbang] Dependencies resolved
[jbang] Building jar for qrcode.java...
[jbang] Post build with org.graalvm.python.embedding.tools.jbang.JBangIntegration

real    2m13.024s
user    4m57.199s
sys     0m10.572s

The first run took 2+ minutes to complete. The second run finished in 11 seconds.

$ time jbang run qrcode.java "Hello from GraalPy!"

real    0m10.973s
user    0m26.484s
sys     0m0.961s

Both times the following warning was printed on the console. This should be further investigated.

[engine] WARNING: The polyglot engine uses a fallback runtime that does not support runtime compilation to native code.
Execution without runtime compilation will negatively impact the guest application performance.
The following cause was found: JVMCI is required to enable optimizations. Pass -XX:+EnableJVMCI as a virtual machine argument to the java executable to resolve this.
For more information see: https://www.graalvm.org/latest/reference-manual/embed-languages/#runtime-optimization-support.
To disable this warning use the '--engine.WarnInterpreterOnly=false' option or the '-Dpolyglot.engine.WarnInterpreterOnly=false' system property.

Experimental run with EnableJVMCI enabled.

$ export JBANG_JAVA_OPTIONS="-XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI"
$ time jbang run qrcode.java "Hello from GraalPy!"

[engine] WARNING: The polyglot engine uses a fallback runtime that does not support runtime compilation to native code.
Execution without runtime compilation will negatively impact the guest application performance.
The following cause was found: No optimizing Truffle runtime found on the module or class-path.
For more information see: https://www.graalvm.org/latest/reference-manual/embed-languages/#runtime-optimization-support.
To disable this warning use the '--engine.WarnInterpreterOnly=false' option or the '-Dpolyglot.engine.WarnInterpreterOnly=false' system property.

real    0m10.893s
user    0m32.548s
sys     0m1.307s

Experimental run with EnableJVMCI enabled and Interpreter Warning set to false.

$ export JBANG_JAVA_OPTIONS="-XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI -Dpolyglot.engine.WarnInterpreterOnly=false"

$ time jbang run qrcode.java "Hello from GraalPy!"

real    0m11.330s
user    0m33.603s
sys     0m1.315s

TBD - test with optimizing Truffle runtime installed / enabled.

[wfouche]

python-jvm@wfouche is a JBang app that streamlines the process of executing GraalPython programs within a JVM environment.

#!/usr/bin/env python-jvm

# restclient_graalpy.py
#
# Run: jbang run python-jvm@wfouche restclient_graalpy.py
#

# /// jbang
# requires-graalpy = "==24.2.1"
# requires-java = ">=21"
# debug = false
# dependencies = [
#   "org.springframework.boot:spring-boot-starter-web:3.4.4"
# ]
# [graalpy]
#   allowAllAccess = true
#   emulateJython = true
# [java]
#   runtime-options = "-XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI -Dpolyglot.engine.WarnInterpreterOnly=false"
# [jbang]
#   integrations = false
# ///

import java.lang.String as String
import org.springframework.web.client.RestClient as RestClient

def restApiCall(uri: str, id: int):
    restClient = RestClient.create()
    rsp = restClient.get().uri(uri, id).retrieve().body(String)
    print(rsp)

def main():
    restApiCall("https://jsonplaceholder.typicode.com/todos/{id}", 1)

main()

Output:

{
  "userId": 1,
  "id": 1,
  "title": "delectus aut autem",
  "completed": false
}

[wfouche]

Running python-jvm without any parameters will start the Jython interpreter.

$ jbang run python-jvm@wfouche
python-jvm/1/2025-04-24T17:58:24
Jython 2.7.4 (tags/v2.7.4:3f256f4a7, Aug 18 2024, 10:30:53)
[OpenJDK 64-Bit Server VM (Eclipse Adoptium)] on java21.0.6
Type "help", "copyright", "credits" or "license" for more information.
>>> 
>>> print(1+1)
2
>>> 
>>>