Send a string as a parameter in python subprocess

According to this answer I can execute the .bat file in Python. Is it possible not only execute .bat file, but also send a string as a parameter, which will be used in Java programm?

What I have now:

Python script:

import subprocess

filepath="C:/path/to/batch/myBatch.bat"
p = subprocess.Popen(filepath, shell=True, stdout = subprocess.PIPE)

stdout, stderr = p.communicate()
print p.returncode # is 0 if success

Java programm:

public static void main(String[] args) {
    System.out.println("Hello world");
}

What I want to have:

Python script:

import subprocess

parameter = "C:\\path\\to\\some\\file.txt"
filepath="C:/path/to/batch/myBatch.bat"
p = subprocess.Popen(filepath, shell=True, stdout = subprocess.PIPE, parameter)

stdout, stderr = p.communicate()
print p.returncode # is 0 if success

Java programm:

public static void main(String[] args) {
    System.out.println("Hello world");
    System.out.println(args[1]); // prints 'C:\\path\\to\\some\\file.txt'
}

So the main idea is to send a string from python as parameter to a java programm and use it. What I have tried is following:

import os
import subprocess

filepath = "C:\\Path\\to\\file.bat"
p = subprocess.Popen(filepath, shell=True, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
grep_stdout = p.communicate(input=b"os.path.abspath('.\\file.txt')")[0]
print(grep_stdout.decode())
print(p.returncode)
print(os.path.abspath(".\\file.txt"))

Output:

1
C:\\path\\to\\file.txt

1 means, that something went wrong. And it is so, because Java programm looks like this:

public static void main(String[] args) throws IOException {
    String s = args[1];
    // write 's' to a file, to see the result
    FileOutputStream outputStream = new FileOutputStream("C:\\path\\to\\output.txt");
    byte[] strToBytes = s.getBytes();
    outputStream.write(strToBytes);
    outputStream.close();
}

and after execution file.bat in Python, output.txt is empty. What am I doing wrong?