如何在Scala中调用Python脚本并获取输出？

Got it, let's fix this! The issue with your current code is that the ! method on a ProcessBuilder only returns the exit status code of the process, not the actual output from your Python script. Here are a few straightforward ways to capture that output in Scala:

1. Use the !! method (simplest approach) #

The !! method executes the command and returns the entire standard output as a String. It's the quickest way if you just need the output and don't need to handle error streams separately:

import scala.sys.process._

// Execute the script and capture output
val output = "python3 runner.py" !!

// Print the captured output
println(output) // Will print "testing"

Note: If the Python script exits with a non-zero status code, !! will throw an exception. If you want to handle this gracefully, you can use the overloaded version that takes a ProcessLogger to capture errors.

2. Use ProcessIO for fine-grained control #

If you need to separate standard output and error output, or handle large streams without buffering everything into memory, use ProcessIO:

import scala.sys.process._

val stdout = new StringBuilder
val stderr = new StringBuilder

// Execute the script and capture both streams
val exitCode = "python3 runner.py" ! ProcessIO(
  in => in.close(), // We don't need to send input to the Python script
  out => {
    // Read standard output line by line
    scala.io.Source.fromInputStream(out).getLines().foreach(line => stdout.append(line + "\n"))
    out.close()
  },
  err => {
    // Read error output line by line
    scala.io.Source.fromInputStream(err).getLines().foreach(line => stderr.append(line + "\n"))
    err.close()
  }
)

// Print results
println(s"Exit Code: $exitCode")
println(s"Standard Output:\n$stdout")
println(s"Error Output:\n$stderr")

3. Use Java's ProcessBuilder with Scala's Source #

You can also combine Java's low-level ProcessBuilder with Scala's Source to read the output:

import scala.io.Source

// Start the Python process
val process = new ProcessBuilder("python3", "runner.py").start()

// Read standard output
val output = Source.fromInputStream(process.getInputStream).mkString

// Wait for the process to finish and get exit code
val exitCode = process.waitFor()

// Print results
println(s"Exit Code: $exitCode")
println(s"Output: $output")

This approach gives you full control over the process lifecycle, which is useful for more complex scenarios.

Quick Notes: #

• Make sure runner.py is in your working directory, or use the full path to the script (e.g., /home/user/scripts/runner.py).
• If your output includes non-ASCII characters, specify the encoding when reading the stream (e.g., Source.fromInputStream(out, "UTF-8")).

内容的提问来源于stack exchange，提问作者user15609698