How to execute a python file with few arguments in java

Question

String command:

python FileName.py <ServerName> userName pswd<b>

---

Process p = Runtime.getRuntime().exec(command);
BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = "";
while ((line = reader.readLine()) != null) {
    System.out.println(line + "\n");
}

Code is not terminating nor giving the results

Answer 1

You can use Java Runtime.exec() to run python script, As an example first create a python script file using shebang and then set it executable.

#!/usr/bin/python
import sys
print ('Number of Arguments:', len(sys.argv), 'arguments.')
print ('Argument List:', str(sys.argv))
print('This is Python Code')
print('Executing Python')
print('From Java')

if you save the above file as script_python and then set the execution permissions using

chmod 777 script_python

Then you can call this script from Java Runtime.exec() like below

import java.io.*;
import java.nio.charset.StandardCharsets;

public class ScriptPython {
       Process mProcess;

public void runScript(){
       Process process;
       try{
             process = Runtime.getRuntime().exec(new String[]{"script_python","arg1","arg2"});
             mProcess = process;
       }catch(Exception e) {
          System.out.println("Exception Raised" + e.toString());
       }
       InputStream stdout = mProcess.getInputStream();
       BufferedReader reader = new BufferedReader(new InputStreamReader(stdout,StandardCharsets.UTF_8));
       String line;
       try{
          while((line = reader.readLine()) != null){
               System.out.println("stdout: "+ line);
          }
       }catch(IOException e){
             System.out.println("Exception in reading output"+ e.toString());
       }
}
}

class Solution {
      public static void main(String[] args){
          ScriptPython scriptPython = new ScriptPython();
          scriptPython.runScript();
      }

}

Hope this helps and if not then its recommended to join our Java training class and learn about Java in detail.

Comments

I was getting exception while running Java code. So I modified the one line:

process = Runtime.getRuntime().exec(new String[]{"python", "script_python","arg1","arg2"});

Now the program is running without error.

Answer 2

There are three ways to get this done:

• runtime approach
• process approach
• jython approach

Have a look at this blog for detailed explanation with example.

Comments

Sorry None of those approaches are usefull

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Hey there! Share the code you have used and the error you are getting..

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This is the code that worked for me:

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yes this solution is working fine

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 Omkar, This code run in command prompt but it cant work on netbeans 

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Thankyou bro, it works

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its working but  not showing output?

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Hey, @There,

Are you getting any error or getting just blank space as output? Can you please confirm in brief!

Answer 3

how to read pandas dataframe in java

Comments

Hey! It would be better if you post this as a new question. Because your question is irrelevant to this thread. And also, by posting this as a new question, more people will be able to help you.

Answer 4

In short one solution could be:

public void runPython() 
{ //need to call myscript.py and also pass arg1 as its arguments.
  //and also myscript.py path is in C:\Demo\myscript.py

    String[] cmd = {
      "python",
      "C:/Demo/myscript.py",
      this.arg1,
    };
    Runtime.getRuntime().exec(cmd);
}

edit: just make sure you change the variable name from str to something else, as noted by cdarke

Your python code (change str to something else, e.g. arg and specify a path for file):

def returnvalue(arg) :
    if arg == "hi" :
        return "yes"
    return "no"
print("calling python function with parameters:")
print(sys.argv[1])
arg = sys.argv[1]
res = returnvalue(arg)
print(res)
with open("C:/path/to/where/you/want/file.txt", 'w') as target:  # specify path or else it will be created where you run your java code
    target.write(res)