Accessing one function written in Python from Java or C# that returns an array

Question

I have one piece of code written in Python 3. Inside of it I have this function:

def a_star(matrix, start, goal):

It uses this 2 libraries to work:

import numpy
from heapq import *

And returns an array.

But the program must have a GUI and in Python implementing it is hard and ugly.

I just want to execute that function from other program (using Java or C#) how can I do that?

Thanks

You'd have to embed Python in Java or C#. It would most likely be easier just to rewrite that function in Java or C# however. — vallentin
– vallentin, Commented Apr 28, 2017 at 2:48
yep, but the the function is really a messy code I don't really understand how it works. So is not a simplest way? what if the hole python program returns only a string in console? is that easy? — Iván E. Sánchez
– Iván E. Sánchez, Commented Apr 28, 2017 at 2:51
Try to read (example 1)[stackoverflow.com/questions/33004907/… & (example 2)[stackoverflow.com/questions/33669450/… for C#, then (example 3)[stackoverflow.com/questions/16447410/… & (example 4)[stackoverflow.com/questions/9006520/… for Java. — Tetsuya Yamamoto
– Tetsuya Yamamoto, Commented Apr 28, 2017 at 3:29
Python's Tkinter is not that bad for UI, have you really taken a look? It's definitely not worse than Swing :) Anyway, I'd agree with @Vallentin. — Josep Valls
– Josep Valls, Commented Apr 28, 2017 at 3:30

Peeyush · Accepted Answer · 2017-04-28 06:07:39Z

0

As all of these programming languages use their own programming models it would not be possible to directly call any function written in one language from another language. In this case, however, if your Python application supports SOAP or HTTP based service calls then you can still achieve it.

answered Apr 28, 2017 at 6:07

Peeyush

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TCS · Accepted Answer · 2024-09-02 08:00:59Z

You can use MetaFFI to do that.

As I don't know the types of "start" and "goal", I'll just refer to using numpy directly from Java, but you can also use MetaFFI to load your own function.

Let's say I want to load an array and calculate its mean, just to make a simple example.

// load python3.11 runtime
MetaFFIRuntime runtime = new MetaFFIRuntime("python311");
runtime.loadRuntimePlugin();

// load numpy package (assume it has been installed by PIP)
MetaFFIModule np = runtime.loadModule("numpy");

// load array constructor
Caller constructor = np.load("callable=array",
                // parameters
                new MetaFFITypeInfo[]{new MetaFFITypeInfo(MetaFFITypes.MetaFFIInt64Array, 1)},
                // return values
                new MetaFFITypeInfo[]{new MetaFFITypeInfo(MetaFFITypes.MetaFFIHandle)});

// load mean method
Caller pmean = np.load("callable=ndarray.mean,instance_required",
                new MetaFFITypeInfo[]{new MetaFFITypeInfo(MetaFFITypes.MetaFFIHandle)},
                new MetaFFITypeInfo[]{new MetaFFITypeInfo(MetaFFITypes.MetaFFIFloat64)});

// create our numpy array
var input = new long[]{1,2,3,4};
MetaFFIHandle numpyarr = (MetaFFIHandle)constructor.call((Object)input)[0];

// call mean method
double meanres = (double)(pmean.call(numpyarr)[0]);


/*
You can also get a string representation of the array by loading __str__():

// load __str__ just so we can print nicely the results
Caller pstr = np.load("callable=ndarray.mean.__str__,instance_required",
                new MetaFFITypeInfo[]{new MetaFFITypeInfo(MetaFFITypes.MetaFFIHandle)},
                new MetaFFITypeInfo[]{new MetaFFITypeInfo(MetaFFITypes.MetaFFIString8)});
*/

Disclaimer: I am the author of MetaFFI

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