Alex Gamela

25. februar 2024

Min Read

Jython vs Python: Vigtigste forskelle, og hvornår de skal bruges

Jython og Python er to versioner af det samme sprog, der bruges til forskellige sammenhænge. Jython er en Java-implementering af Python, hvilket i en nøddeskal betyder, at det er Python, der kører på et Java Virtual Machine (JVM) miljø. Det skriver som Python, men det kan få adgang til det fulde potentiale i Java-biblioteker.

Vi kigger på Forskelle mellem Jython og Python og hvorfor Jython bliver stadig mere populært blandt Java- og Python-udviklere, der lærer at bruge denne implementering i sammenhæng med JVM'er til at forbedre produktiviteten og opnå hurtigere resultater.

I stedet for at diskutere, hvilken der er bedre, da de deler de samme kernefunktioner, viser vi hvordan at forbinde Python til Java gennem Jython åbner en helt ny verden af muligheder.

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Hvad er Python?

„Python“ refererer til det originale C-baserede programmeringssprog, så når du læser Python, betyder det CPython. Det blev så populært, at C blev underforstået, idet Python var den fælles betegnelse og referencen, som alle de forskellige implementeringer sammenlignes med.

Python er et af de mest populære objektorienterede programmeringssprog, ofte sammenlignet med Perl, Rubyog Java. Python er meget værdsat på grund af sin syntaks enkelhed og læsbarhed, hurtigere udvikling og kraftfulde applikationer.

Programming languages' ranking, with Javascript being the most popular
Kilde: GitHub Octoverse

Pythons vigtigste funktioner er:

Syntaks - Python er let at skrive, læse og forstå, hvilket gør det ideelt at bygge prototyper og fremskynde udviklingsprocessen. Dens klarhed og kortfattethed gør det til et ideelt sprog for begyndere.‍

Ansøgninger - Det kan være velegnet til at starte med programmering, men Python har et avanceret applikationspotentiale. Python er udbredt bruges i datavidenskab, maskinlæring, datavisualisering og databehandling.‍

Biblioteker - Kraften i Python ligger i de tilgængelige biblioteker, der dækker de mest almindelige programmeringsopgaver såsom at oprette forbindelse til webservere, læse og ændre filer, søge tekst med regulære udtryk og nogle mere avancerede bestræbelser som maskinlæring.‍

Nemt at udvide - udviklere kan udvide funktionerne i Python ved at tilføje nye moduler kompileret i C, ved at indlejre det i applikationer eller ved at gruppere selve koden i moduler og pakker til genbrug.‍

Kompatibilitet - Python kører i alle operativsystemer: Mac OS X, Windows, Linux og Unix. Android og iOS kommer også på listen takket være uofficielle opbygninger.‍

Gratis - Som de bedste ting i livet koster Python ikke noget. Alle kan downloade og bruge Python i deres applikationer. Og da det er tilgængeligt under en open source-licens, kan det også frit ændres og omdistribueres.

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Hvad er Java?

Java er også et populært objektorienteret programmeringssprog, med en lignende syntaks som C ++ og C. Det er statisk indtastet, hvilket betyder, at det udfører typekontrol på kompileringstid, i modsætning til Pythons dynamisk typede programmeringssprogskarakteristika.

Kernefunktionerne i Java er:

Syntaks - Javas syntaks ser lidt besværlig ud sammenlignet med Python, ved hjælp af mere kode og med strengere regler. Tilstedeværelsen af parenteser gør det endnu mindre attraktivt og mere tilbøjeligt til valideringsfejl.

Ansøgninger - Java bruges overalt, fra webapplikationer til desktop GUI-apps, virksomhedsapplikationer og integrerede systemer.

Biblioteker - Der er et stort antal Java-biblioteker til rådighed Det kan bruges til næsten alt.

Udvidelser - Javas kernefunktioner kan udvides gennem et sæt pakker eller klasser bundtet i en JAR-fil.

Kompatibilitet - Java kører i Java Virtual Machine-miljøer, som kan køre i enhver enhed eller operativsystem efter Princippet „Skriv en gang, kør hvor som helst“.

Gratis - Det er gratis og tilgængeligt til generel computing.

For at vide mere om, hvordan Python adskiller sig fra Java, vi anbefaler at læse vores dybdegående sammenligning.

Best agile pracices to use in your software development cycle
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Hvad er Jython?

Nu hvor vi har en idé om, hvad Python og Java er, vil det være lettere at forstå begrebet Jython. Som vi sagde i første omgang, Jython er en Java-implementering af Python, udviklet til at køre i Java-platforme og brug Java-klasser. Selve navnet er en fortælling: Jython = Java+Python.

Det har de fleste af de egenskaber, vi beskrev ovenfor for Python, og åbner nye muligheder for programmører, der kan bruge Pythons syntaks og logik i et Java Virtual Machine (JVM) miljø, med bonusen ved at bruge Javas biblioteker.

Jythons hovedtræk er:

Elegant syntaks - Det deler den samme syntaks som Python og al dens enkelhed, klarhed og kortfattethed.

Ansøgninger - Hovedapplikationen af Jython er integrationen af Java med Python, hvilket gør det muligt for udviklere at bruge JVM-biblioteket, mens de skriver i Python-semantik inden for en Java-platform. Java er en fantastisk ressource til Machine Learning, da det er let at debugge, mens du håndterer store operationer.

Biblioteker - Jython kan bruge alle Java-biblioteker. Det er den mest tiltalende del for Python-udviklere, da de kan få adgang til Java-biblioteker som Deep Learning4J.

Kompatibilitet - Jython kører i enhver Java Virtual Machine, og JVM kører i de fleste enheder, så Jython kører, dybest set, hvor som helst.

Gratis - Jython er tilgængelig til kommerciel og ikke-kommerciel brug.

Jython er broen, der forbinder Java og Pythons verdener, hvilket giver mulighed for problemfri interaktion mellem disse to sprog.

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Forskelle mellem Python og Jython

Python og Jython deler mange af de samme kerneegenskaber. Men Jython gør, hvad Python kan gøre med de ekstra muligheder i Java, hvilket muliggør brugen af en Pythonesque syntaks til at skrive Jython-moduler, der kan udnytte den store mængde Java-biblioteker til applikationsintegration.

Table comparing differences between Python and Jython
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Fordele ved Jython

Nu hvor vi har fastslået, hvad Jython er, hvad det ikke er, og hvad det er godt til, lad os finde ud af, hvorfor det er en så attraktiv mulighed for udviklere overalt. Jython bygger ikke kun bro mellem mulighederne i Python og Java, men skaber også nye.

Det er en nemt programmeringssprog at lære og implementere, der har en masse magt takket være den enorme mængde Java-biblioteker, det bringer. Det kan bruges til at oprette hurtige grafiske brugergrænseflader, kalde til en database, oprette rammer eller teste koden hurtigt for fejl.

Visuelt ser det endda bedre ud. Ligesom Python er Jython afhængig af indrykninger og mellemrum i stedet for parenteser for at opdele kodeblokke og definere struktur, hvilket begrænser tilstedeværelsen af unødvendige symboler i koden.

Lad os sammenligne en simpel if-sætning i Java med den samme i Python/Jython:

Java if-sætning

Python/Jython if-sætning

Sidstnævnte version ser renere, slankere og mere kortfattet ud. Ingen krøllede parenteser, ingen enkelte inverterede kommaer og ingen parenteser. Lighederne med Pythons syntaks gør Jython til et værdifuldt værktøj til at hjælpe programmører med at kode Java-applikationer uden kompleksiteten og kravene til kodning i Java.

Adgang til Javas biblioteker er en anden stor fordel, da der er biblioteker til næsten alt. Programmører kan arbejde hurtigere, hvilket sparer tid i udviklings- og teststadierne.

Jython arbejder også, hvor JVM arbejder. Python-koden, der bruges i en Jython-applikation, kompileres som Java-bytecode, et instruktionssæt skrevet til Java Virtual Machine. Da JVM er designet til at arbejde overalt, fremmer denne funktion portabilitet på tværs af platforme og forbedrer ydeevnen.

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Python+Java = Jython

Så det er ikke en Python vs. Jython-situation, men en vindende sammenslutning af funktioner, der gør Jython en kraftfuld blanding af Python og Java. Jython kombinerer Pythons lethed og alsidighed med Java-universets potentiale, hvilket gør det til en seriøs mulighed for udviklere, der ønsker at dyppe tæerne i højniveau-sprogfarvande ved hjælp af en enklere syntaks.

Enten for Java- eller Python-udviklere kan Jython være værd at se på for at udvide programmeringsmulighederne og skabe kraftfulde applikationer med en elegant syntaks.

På Imaginary Cloud, Vi udvikler elegante løsninger til effektive web- og mobilapplikationer. Vores højt kvalificerede team af front-end-udviklere og UX/UI-designere kan levere de bedste resultater inden for korte tidsrammer. Lad os tale.

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Threading in Jython: no GIL, but real constraints

Concurrency is where Jython has a genuine edge. CPython carries a Global Interpreter Lock (GIL), a mechanism that lets only one thread run Python bytecode at a time, which throttles CPU-bound multithreading. Jython has no GIL. Every Python thread maps to a native Java thread, so heavy compute can actually run in parallel across cores. Standard CPython can't manage that without reaching for multiprocessing.

Is it a free win? Not quite. Jython still takes a module import lock on every import, so tight loops that keep importing inside threaded code pay for it. And because Jython is frozen at Python 2.7, it has none of the concurrency tooling Python 3 brought in. No undefined. No undefined/undefined. None of the nicer undefined ergonomics. Teams building high-concurrency services today expect those Python 3 primitives as standard, and Jython simply can't hand them over.

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The Python 3 compatibility gap

The Python 3 gap goes deeper than a bit of syntax. Jython's lack of Python 3 support means more than ten years of Python 3 features are just missing: f-strings, type hints and the undefined module, undefined/undefined, undefined, undefined, matrix operators, and a long tail of standard-library upgrades. Any code, tutorial, or dependency written for Python 3, which is basically the whole ecosystem now, won't run on Jython as-is.

This is also where the data-science and machine-learning story falls down. NumPy, pandas, PyTorch, TensorFlow: they all lean on CPython's C-extension interface, and Jython doesn't implement it. So Jython can call JVM-based ML libraries like Deeplearning4j, but the mainstream Python ML stack, the very thing that pushed Python to the top of GitHub, stays out of reach.

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Where Jython is used in production

For all that, Jython has carved out a niche it holds comfortably: an embedded scripting engine inside Java applications, where the point is to let people write Python against a running Java system.

  • Enterprise middleware and application servers. Oracle's WebLogic Server ships WLST (WebLogic Scripting Tool), an administration and configuration interface built on Jython, and it's used widely across banking, telecom, and government IT operations.
  • Search and data infrastructure. Apache Solr has supported Jython for writing custom document-processing scripts in its update pipeline.
  • Statistical and scientific tooling. The SPSS statistics platform exposes Jython for scripting and automation, and Jython has been embedded in a range of engineering and analytics tools that run on the JVM.
  • Build, test, and integration scripting. Teams with large Java codebases have long used Jython to write test harnesses and glue code that needs direct, in-process access to Java objects.

The thread running through all of these? Jython earns its place where a Java platform already exists and wants a light scripting layer on top. Not as the ground floor of something new.

Here's the pattern that shapes how we advise clients. In the JVM modernisation work we take on, teams almost never chose Jython. They inherited it. It's like old wiring behind a wall in a house you've just bought. Nobody put it there on purpose, and nobody wants to be the one to touch it. So the real question is rarely "should we adopt Jython?" It's "what does it cost to move off it, and when does that bill come due?" Ask that early, before a Python 3 dependency or a security requirement forces your hand, and a looming migration becomes a planned one. That reframing is the most useful thing we bring to these conversations, and it's the step most teams skip.

Jython vs CPython vs GraalPy: a decision guide

If you need Python and Java working together, Jython isn't your only route anymore. The strongest Jython alternatives now speak Python 3. Chief among them is GraalPy, Oracle's Python runtime built on GraalVM. It's Python 3.12-compliant, runs on the JVM, embeds cleanly in Java, and is actively maintained. Its own benchmarks report pure Python running roughly 4x faster than CPython once JIT-compiled, with experimental support for native extensions like NumPy and PyTorch. For most new JVM-plus-Python projects, GraalPy is the natural successor to Jython.

A quick side-by-side to get your bearings:

Aspect CPython Jython GraalPy
Python version 3.x (current) 2.7 only 3.12-compliant
Runs on the JVM No Yes Yes
Java interop Via a bridge (e.g. JPype) Native, seamless Native, seamless
Maintenance Very active Minimal (2.7.4, Aug 2024) Active (Oracle / GraalVM)
C extensions (NumPy, etc.) Full support None Experimental
Best for Mainstream Python, ML/DS Legacy Py2 + Java integration New Python 3 + Java projects

The Fit-Risk-Horizon lens: how we assess runtime choices at Imaginary Cloud

A feature table tells you what differs. It doesn't tell you what should actually drive the decision. When our engineering teams weigh a Python-on-the-JVM choice, we run it through a simple lens we call Fit-Risk-Horizon (FRH). Three questions, asked in that order, that reliably separate a safe pick from an expensive one.

  1. Fit. What's the actual integration need? Embedding a scripting layer in an existing Java product is one problem. Reusing a handful of Java libraries from a Python codebase is another. Building a brand-new service is a third. Name the need precisely before you name the runtime. More often than not, the poor choices we see start with a runtime hunting for a use case.
  2. Risk. What's the maintenance and security exposure? Weigh release cadence, end-of-life status, and how deep the ecosystem runs. A runtime frozen on Python 2.7, like Jython, carries risk that a table cell reading "Minimal" quietly understates once anything security-sensitive is on the line.
  3. Horizon. How long does this decision have to hold? A six-month internal tool puts up with constraints a five-year platform never could. The longer the horizon, the more heavily maintenance and lock-in should outweigh a bit of short-term convenience.

Run FRH and the rule of thumb turns concrete:

  • Choose CPython when Fit points to Python as the main platform (data science, ML, web backends, automation) and JVM interop is a side note.
  • Choose Jython only when Fit is a real embed-inside-existing-Java case, the Risk from Python 2.7 is contained (internal, low-exposure), and the Horizon is short to medium.
  • Choose GraalPy when Fit needs Python 3 and Java in one runtime, and either Risk or Horizon rules out an end-of-life dialect. For most new builds, it does.

When to use Jython: making the case for Java and Python integration

So, back to where we started. This was never really a "Python vs Jython" contest. It's a question of fit. Jython pairs Python's lightweight syntax with the reach of the Java ecosystem, and for the right job that pairing is genuinely valuable: embedding Python scripting inside a JVM application, reusing Java libraries from Python code, or giving operators a friendly way to steer a Java system.

The honest caveat sits right next to the benefit. Jython's strengths are bolted to Python 2.7 and a slow release cadence. Where you can live with that, usually inside an established Java platform, Jython is still a sensible tool. Where you can't, CPython or GraalPy will treat your team better.

What this means for technical decision-makers

For a CTO, CDO, or engineering lead, the Jython question isn't really about syntax. It's about risk, cost, and delivery timescales. The Fit-Risk-Horizon lens is ordered the way it is on purpose: technical fit is necessary, but it's rarely enough on its own. The decisions that hurt are almost always the ones where risk and horizon got underweighted.

Integration risk. Jython's whole appeal is tight, in-process interoperability between Python and Java. Real capability, genuine pull. But it ties you to a runtime capped at Python 2.7. Any roadmap that assumes the modern Python 3 ecosystem (current libraries, security patches, engineers who already know Python 3) is heading straight for that ceiling.

Team upskilling and hiring. New engineers learn Python 3 and expect Python 3. In Stack Overflow's 2024 Developer Survey, Python was used by 51% of developers and ranked as the single most-desired language, while Python 2 has all but vanished from professional practice. That same survey pegged technical debt as developers' number-one workplace frustration. Standardising on an end-of-life dialect is technical debt by definition. In plain terms: a narrower hiring pool, slower onboarding, weaker retention. The upskilling cost runs the wrong way.

Maintenance exposure. Put real numbers on it. Python 2.7 hit official end-of-life on 1 January 2020, so that's more than five years with no upstream security or bug fixes. Jython's cadence tells the same story: 2.7.2 in 2020, 2.7.3 in 2022, 2.7.4 in August 2024. Roughly one release every two years, from a small volunteer team. Fine for a stable embedded scripting layer. A poor footing for a system you expect to grow and secure over a five-to-ten-year horizon, where the whole maintenance and patch burden lands on you.

Return on investment and time-to-value. The commercial case rarely hinges on raw performance, though the direction of travel is worth a glance: GraalPy reports pure Python running roughly 4x faster than CPython, with Python 3 and native Java interop in a single runtime. The bigger ROI lever is when you decide. Pick the runtime at the design stage and it's a scoped, estimable task. Trip over the constraint mid-delivery, when a required Python 3 library or an audit finding or a security patch forces it, and you've got an unplanned migration elbowing its way into the roadmap and pushing time-to-value back. The cheapest migration is the one you plan before you need it.

Timescales and lock-in. This choice bites hardest at the architectural forks. Reach for Jython on a greenfield service and you can quietly lock yourself into Python 2 semantics that cost real money to unwind later. If Python and Java interoperability is a true requirement, weigh GraalPy up front, well before a migration turns urgent. That protects your timescales and keeps your options open. It's exactly the trade-off competing pages tend to skate past, and it's the one most likely to hit delivery risk.

Sizing the cost: what actually drives a move off Jython

For budgeting, the cost of leaving Jython isn't one number. It scales with a handful of concrete factors, and naming them beats quoting a headline figure you'd only have to caveat. In our experience, the big swing variables are these:

  • Codebase size and coupling: a few hundred lines of Python glue calling Java is a person-days job. A service with deep, two-way Java interop is a person-months one.
  • Test coverage: solid automated tests make a runtime swap fast and low-risk. Their absence is usually the single biggest hidden cost, because every behaviour has to be re-checked by hand.
  • Dependency profile: pure-Python and JVM-library code ports most easily. Anything leaning on CPython C extensions needs replacing or reworking.
  • Python 2-to-3 language debt: print statements, integer division, string and bytes handling. Mechanical changes, but they're everywhere. Tooling automates a lot of it, though not all.
  • Target runtime: move to GraalPy and you keep your Java interop, which shortens the path. Move to CPython and you may be re-architecting the Java boundary through a bridge.

The commercial takeaway is simple. Cost is driven by test coverage and interop depth, not by the language switch itself. Which is why a short, scoped assessment up front is worth far more than a rule-of-thumb guess, and why the teams that get burned are the ones that only price the migration once it's already unavoidable.

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Frequently asked questions

Is Jython still maintained?

Yes, but only just. The most recent stable release was 2.7.4 in August 2024, from a small volunteer team, and releases tend to land years apart. It's alive enough to keep existing Python 2 integrations running, but it isn't under active feature development.

Does Jython support Python 3?

No. Every stable Jython release supports Python 2.7 only. A Python 3 version has been discussed for years but doesn't exist, and the project itself advises against treating Jython as a substitute for porting to Python 3.

When should I use Jython instead of Python (CPython)?

Use Jython when you need to embed Python scripting inside an existing Java application, or call Java libraries directly and in-process, and when Python 2.7 is acceptable. For nearly everything else, especially data science, machine learning, or new Python 3 work, standard CPython is the better call.

What is the difference between Jython and CPython?

CPython is the reference Python implementation: written in C, currently on Python 3.x, and compatible with the full PyPI and C-extension ecosystem. Jython is written in Java, compiles Python to Java bytecode, runs on the JVM, supports Python 2.7 only, and can use Java libraries but not CPython C extensions. That's the Jython vs CPython split in a nutshell.

Can Jython use Python libraries like NumPy or pandas?

No. NumPy, pandas, PyTorch, and the like depend on CPython's C-extension interface, which Jython doesn't implement. It can, however, call JVM-based libraries such as Deeplearning4j.

Does Jython have the Global Interpreter Lock (GIL)?

No. Unlike CPython, Jython has no GIL, so Python threads map to native Java threads and can run in true parallel across CPU cores. It does still use a module import lock, and it lacks Python 3 concurrency tools like asyncio.

What is a modern alternative to Jython?

GraalPy, Oracle's GraalVM-based runtime, is a Python 3.12-compliant implementation that runs on the JVM, embeds in Java, and is actively maintained. For new projects that need Python and Java in one runtime, it's generally the stronger option.

Is Jython free to use?

Yes. Jython is open source and available for both commercial and non-commercial use.

If your team is weighing up whether to bring Python workflows into a Java platform, we can help you assess the technical fit and the delivery risk, right down to whether Jython, GraalPy, or standard CPython is the right foundation for your roadmap. Tell us where you are in the process.

Alex Gamela
Alex Gamela

Indholdsforfatter og digital medieproducent med interesse i det symbiotiske forhold mellem teknologi og samfund. Bøger, musik, og guitarer er en konstant.

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