How Can I Successfully Retrieve Return Values from a Python Function Called by a Go Program?

Calling Python Functions from Go and Retrieving Return Values

One common task when working with multiple languages in a project is the ability to invoke functions from one language within another. In this case, we're exploring how to call a Python function from a Go program and retrieve its return value.

Original Attempt and Issue

In an initial attempt, the following Go code was used:

package main

import (
    "fmt"
    "os/exec"
)

func main() {
    cmd := exec.Command("python", "-c", fmt.Sprintf("'import pythonfile; print pythonfile.cat_strings(\"%s\", \"%s\")'", "foo", "bar"))
    out, err := cmd.CombinedOutput()
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(out))
}

However, this approach encountered an issue where the return value from the Python function was not being captured in the Go program. The output showed an empty string, " ".

Problem Analysis

The problem arose due to the way the Python command was formatted. The quotes surrounding the command itself were leading to the Python interpreter treating the command as a single string instead of a list of arguments.

Solution

To resolve the issue, the quotes surrounding the command were removed. The following Go code demonstrates the solution:

package main

import (
    "fmt"
    "os/exec"
)

func main() {
    cmd := exec.Command("python", "-c", "import pythonfile; print pythonfile.cat_strings('foo', 'bar')")
    out, err := cmd.CombinedOutput()
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(out))
}

By removing the quotes, the command is now executed as intended, and the return value from the Python function can be properly captured in the Go program.

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