问题:在Java中调用Python?

我想知道是否可以使用jython从Java代码调用python函数,还是仅用于从python调用Java代码?

I am wondering if it is possible to call python functions from java code using jython, or is it only for calling java code from python?


回答 0

Jython:适用于Java平台的Python- http ://www.jython.org/index.html

您可以使用Jython从Java代码轻松调用python函数。只要您的python代码本身在jython下运行,即不使用某些不受支持的c扩展名。

如果这对您有用,那肯定是您可以获得的最简单的解决方案。否则,您可以使用org.python.util.PythonInterpreter新的Java6解释器支持。

我的脑海中有一个简单的例子-但我希望它可以工作:(为简便起见,没有进行错误检查)

PythonInterpreter interpreter = new PythonInterpreter();
interpreter.exec("import sys\nsys.path.append('pathToModules if they are not there by default')\nimport yourModule");
// execute a function that takes a string and returns a string
PyObject someFunc = interpreter.get("funcName");
PyObject result = someFunc.__call__(new PyString("Test!"));
String realResult = (String) result.__tojava__(String.class);

Jython: Python for the Java Platform – http://www.jython.org/index.html

You can easily call python functions from Java code with Jython. That is as long as your python code itself runs under jython, i.e. doesn’t use some c-extensions that aren’t supported.

If that works for you, it’s certainly the simplest solution you can get. Otherwise you can use org.python.util.PythonInterpreter from the new Java6 interpreter support.

A simple example from the top of my head – but should work I hope: (no error checking done for brevity)

PythonInterpreter interpreter = new PythonInterpreter();
interpreter.exec("import sys\nsys.path.append('pathToModules if they are not there by default')\nimport yourModule");
// execute a function that takes a string and returns a string
PyObject someFunc = interpreter.get("funcName");
PyObject result = someFunc.__call__(new PyString("Test!"));
String realResult = (String) result.__tojava__(String.class);

回答 1

嘿,我想我会输入我的答案,尽管已经很晚了。我想首先要考虑一些重要的事情,即您希望在java和python之间建立多强的连接。

首先 ,您是否只想调用函数,或者您是否真的希望python代码更改Java对象中的数据?这个非常重要。如果您只想调用带或不带参数的python代码,那并不是很难。如果您的参数是基元,那么它将变得更加容易。但是,如果您想让Java类在python中实现成员函数,这些成员函数会更改java对象的数据,那么这并不是那么容易或直接的。

其次,我们在谈论cpython还是jython做?我会说cpython是它的所在!我主张这就是为什么python如此强大的原因!但是,在需要时具有如此高的抽象度却可以访问c,c ++。想象一下您是否可以在Java中使用它。这个问题甚至都不值得问jython是否还可以,因为这样很容易。

因此,我使用以下方法,并从容易到困难列出了它们:

Java到Jython

优点:轻而易举。实际引用Java对象

缺点:没有CPython,非常慢!

来自Java的Jython非常简单,如果确实够了,那就太好了。但是它非常慢并且没有cpython!没有cpython值得生活,我不这么认为!您可以轻松地让python代码为java对象实现成员函数。

通过Pyro从Java到Jython到CPython

Pyro是python的远程对象模块。您在cpython解释器上有一些对象,您可以向其发送通过序列化传输的对象,也可以通过此方法返回对象。请注意,如果您从jython发送一个序列化的python对象,然后调用某些函数来更改其成员中的数据,那么您将在java中看不到这些更改。您只需要记住从pyro发送回想要的数据。我相信这是进入cpython的最简单方法!您不需要任何jni或jna或swig或…。您不需要了解任何c或c ++。酷吧?

优点:访问cpython,不像以下方法那样困难

缺点:无法直接从python更改java对象的成员数据。有点间接,(jython是中间人)。

通过JNI / JNA / SWIG将Java转换为C / C ++,通过嵌入式解释器转换为Python(也许使用BOOST库?)

OMG这种方法不适合胆小的人。我可以告诉您,用一种体面的方法来实现这一目标已经花了我很长时间。您要执行此操作的主要原因是,您可以运行cpython代码,以完全控制您的java对象。在决定尝试使用python(就像一匹马)为java(像黑猩猩)做面包之前,需要考虑一些主要的主要事情。首先,如果您崩溃的解释器为您的程序点亮了!而且不要让我开始讨论并发问题!另外,还有锅炉分配器,我相信我已经找到了使该锅炉最小化的最佳配置,但仍然是分配器!那么该怎么做:考虑一下C ++是您的中间人,您的对象实际上就是c ++对象!很好,您现在就知道。只需编写您的对象,就好像您的程序在cpp中而不是java中一样,您想从两个世界访问的数据。然后,您可以使用名为swig(http://www.swig.org/Doc1.3/Java.html),以使Java可以访问此文件并编译一个dll,您可以在java中调用System.load(此处为dll名称)。首先使此工作正常,然后继续进行困难的工作!要使用python,您需要嵌入一个解释器。首先,我建议您编写一些hello解释程序或本教程 python嵌入C / C中。一旦完成这项工作,就该让马和Monkey跳舞了!您可以通过[boost] [3]将c ++对象发送给python。我知道我没有给你鱼,只是告诉你在哪里可以找到鱼。编译时需要注意的一些指针。

编译boost时,您将需要编译一个共享库。并且您需要包括并链接到jdk中所需的内容,即jawt.lib,jvm.lib(启动应用程序时,您的路径中还将需要客户端jvm.dll)以及python27.lib或以及boost_python-vc100-mt-1_55.lib。然后包括Python / include,jdk / include,boost,并且仅使用共享库(dll),否则boost有眼泪。是的,我知道。有很多方法可以解决此问题。因此,请确保您一步一步地完成每件事。然后将它们放在一起。

Hey I thought I would enter my answer to this even though its late. I think there are some important things to consider first with how strong you wish to have the linking between java and python.

Firstly Do you only want to call functions or do you actually want python code to change the data in your java objects? This is very important. If you only want to call some python code with or without arguments, then that is not very difficult. If your arguments are primitives it makes it even more easy. However if you want to have java class implement member functions in python, which change the data of the java object, then this is not so easy or straight forward.

Secondly are we talking cpython or will jython do? I would say cpython is where its at! I would advocate this is why python is so kool! Having such high abstractions however access to c,c++ when needed. Imagine if you could have that in java. This question is not even worth asking if jython is ok because then it is easy anyway.

So I have played with the following methods, and listed them from easy to difficult:

Java to Jython

Advantages: Trivially easy. Have actual references to java objects

Disadvantages: No CPython, Extremely Slow!

Jython from java is so easy, and if this is really enough then great. However it is very slow and no cpython! Is life worth living without cpython I don’t think so! You can easily have python code implementing your member functions for you java objects.

Java to Jython to CPython via Pyro

Pyro is the remote object module for python. You have some object on a cpython interpreter, and you can send it objects which are transferred via serialization and it can also return objects via this method. Note that if you send a serialized python object from jython and then call some functions which change the data in its members, then you will not see those changes in java. You just need to remember to send back the data which you want from pyro. This I believe is the easiest way to get to cpython! You do not need any jni or jna or swig or …. You don’t need to know any c, or c++. kool huh?

Advantages: Access to cpython, not as difficult as following methods

Disadvantages: Cannot change the member data of java objects directly from python. Is somewhat indirect, (jython is middle man).

Java to C/C++ via JNI/JNA/SWIG to Python via Embedded interpreter (maybe using BOOST Libraries?)

OMG this method is not for the faint of heart. And I can tell you it has taken me very long to achieve this in with a decent method. Main reason you would want to do this is so that you can run cpython code which as full rein over you java object. There are major major things to consider before deciding to try and bread java (which is like a chimp) with python (which is like a horse). Firstly if you crash the interpreter that’s lights out for you program! And don’t get me started on concurrency issues! In addition, there is allot allot of boiler, I believe I have found the best configuration to minimize this boiler but still it is allot! So how to go about this: Consider that C++ is your middle man, your objects are actually c++ objects! Good that you know that now. Just write your object as if your program as in cpp not java, with the data you want to access from both worlds. Then you can use the wrapper generator called swig (http://www.swig.org/Doc1.3/Java.html) to make this accessible to java and compile a dll which you call System.load(dll name here) in java. Get this working first, then move on to the hard part! To get to python you need to embed an interpreter. Firstly I suggest doing some hello interpreter programs or this tutorial Embedding python in C/C. Once you have that working, its time to make the horse and the monkey dance! You can send you c++ object to python via [boost][3] . I know I have not given you the fish, merely told you where to find the fish. Some pointers to note for this when compiling.

When you compile boost you will need to compile a shared library. And you need to include and link to the stuff you need from jdk, ie jawt.lib, jvm.lib, (you will also need the client jvm.dll in your path when launching the application) As well as the python27.lib or whatever and the boost_python-vc100-mt-1_55.lib. Then include Python/include, jdk/include, boost and only use shared libraries (dlls) otherwise boost has a teary. And yeah full on I know. There are so many ways in which this can go sour. So make sure you get each thing done block by block. Then put them together.


回答 2

在Java中包含python代码并不明智。用flask或其他Web框架包装您的python代码,使其成为微服务。使您的Java程序能够调用此微服务(例如,通过REST)。

相信我,这很简单,可以为您节省很多问题。而且代码是松散耦合的,因此它们是可伸缩的。

于2020年3月24日更新:根据@stx的评论,上述方法不适用于客户端和服务器之间的海量数据传输。这是我推荐的另一种方法:使用Rust连接Python和Java(也可以使用C / C ++)。 https://medium.com/@shmulikamar/https-medium-com-shmulikamar-connecting-python-and-java-with-rust-11c256a1dfb0

It’s not smart to have python code inside java. Wrap your python code with flask or other web framework to make it as a microservice. Make your java program able to call this microservice (e.g. via REST).

Beleive me, this is much simple and will save you tons of issues. And the codes are loosely coupled so they are scalable.

Updated on Mar 24th 2020: According to @stx’s comment, the above approach is not suitable for massive data transfer between client and server. Here is another approach I recommended: Connecting Python and Java with Rust(C/C++ also ok). https://medium.com/@shmulikamar/https-medium-com-shmulikamar-connecting-python-and-java-with-rust-11c256a1dfb0


回答 3

有几个答案提到您可以使用JNI或JNA来访问cpython,但我不建议您从头开始,因为已经有了用于从java访问cpython的开源库。例如:

Several of the answers mention that you can use JNI or JNA to access cpython but I would not recommend starting from scratch because there are already open source libraries for accessing cpython from java. For example:


回答 4

这里是一个库,可让您一次编写python脚本并确定在运行时使用哪种集成方法(Jython,CPython / PyPy(通过Jep和Py4j)):

https://github.com/subes/invesdwin-context-python

由于每种方法都有其自身的优点/缺点,如链接中所述。

Here a library that lets you write your python scripts once and decide which integration method (Jython, CPython/PyPy via Jep and Py4j) to use at runtime:

https://github.com/subes/invesdwin-context-python

Since each method has its own benefits/drawbacks as explained in the link.


回答 5

这取决于您对python函数的含义是什么?如果它们是用cpython编写的,则不能直接调用它们,则必须使用JNI,但是如果它们是用Jython编写的可以轻松地从Java调用它们,因为jython最终会生成Java字节码。

现在,当我说用cpython或jython编写时,这没有多大意义,因为python是python,并且除非您使用依赖于cpython或java的特定库,否则大多数代码都可以在两种实现上运行。

请参阅此处如何在Java中使用Python解释器。

It depends on what do you mean by python functions? if they were written in cpython you can not directly call them you will have to use JNI, but if they were written in Jython you can easily call them from java, as jython ultimately generates java byte code.

Now when I say written in cpython or jython it doesn’t make much sense because python is python and most code will run on both implementations unless you are using specific libraries which relies on cpython or java.

see here how to use Python interpreter in Java.


回答 6

根据您的要求,诸如XML-RPC之类的选项可能会很有用,它可以用于虚拟地以任何支持协议的语言远程调用函数。

Depending on your requirements, options like XML-RPC could be useful, which can be used to remotely call functions virtually in any language supporting the protocol.


回答 7

GraalVM是一个不错的选择。我已经完成了与GraalVM的Java + Javascript组合用于微服务设计(具有Javascript反射功能的Java)。他们最近增加了对python的支持,我想尝试一下,尤其是多年来这些社区的规模。

GraalVM is a good choice. I’ve done Java+Javascript combination with GraalVM for microservice design (Java with Javascript reflection). They recently added support for python, I’d give it a try especially with how big its community has grown over the years.


回答 8

您可以使用Java Native Interface从Java调用任何语言

You can call any language from java using Java Native Interface


回答 9

Jython有一些限制:

有许多差异。首先,Jython程序不能使用用C编写的CPython扩展模块。这些模块通常具有扩展名为.so,.pyd或.dll的文件。如果要使用这样的模块,则应寻找用纯Python或Java编写的等效模块。尽管在技术上支持此类扩展是可行的-IronPython这样做-在Jython中尚无计划这样做。

使用Jython将我的Python脚本作为JAR文件分发吗?

您只需使用Runtime或ProcessBuilder从Java调用python脚本(或bash或Perl脚本),然后将输出传递回Java:

在Java中运行bash shell脚本

在Java中运行命令行

java runtime.getruntime()从执行命令行程序获取输出

Jython has some limitations:

There are a number of differences. First, Jython programs cannot use CPython extension modules written in C. These modules usually have files with the extension .so, .pyd or .dll. If you want to use such a module, you should look for an equivalent written in pure Python or Java. Although it is technically feasible to support such extensions – IronPython does so – there are no plans to do so in Jython.

Distributing my Python scripts as JAR files with Jython?

you can simply call python scripts (or bash or Perl scripts) from Java using Runtime or ProcessBuilder and pass output back to Java:

Running a bash shell script in java

Running Command Line in Java

java runtime.getruntime() getting output from executing a command line program


回答 10

这样可以很好地概述当前的选项。其中一些在其他答案中被命名。在他们决定实现Python 3.x之前,Jython不可用,并且许多其他项目都来自python方面并希望访问java。但是,还有一些选项可以命名尚未命名的名称:gRPC

This gives a pretty good overview over the current options. Some of which are named in other answers. Jython is not usable until they decide to implement Python 3.x and many of the other projects are coming form the python side and want to access java. But there are a few options still, to name something which has not been named yet: gRPC


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