将Preg替换为空格，但仅替换单个空格

preg_replace('/(?<!\S)Preg(?!\S)/', ' ', $string);

import re

string = "This is a Preg test."
result = re.sub(r'(?<!\S)Preg(?!\S)', ' ', string)
print(result)

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class Main {
    public static void main(String[] args) {
        String string = "This is a Preg test.";
        String result = string.replaceAll("(?<!\\S)Preg(?!\\S)", " ");
        System.out.println(result);
    }
}

let string = "This is a Preg test.";
let result = string.replace(/(?<!\S)Preg(?!\S)/g, ' ');
console.log(result);