How Can I Retrieve the Return Value of a Python Function Called from a Go Program?

Calling Python Functions from Go with Return Value Retrieval

In this scenario, we aim to bridge the gap between Go and Python by invoking a Python function from a Go program and capturing its return value for further processing. However, initial attempts have proved unsuccessful in retrieving the desired data.

The Stumbling Block

The minimal example provided illustrates the challenge:

package main

import (
    "fmt"
    "os/exec"
)

func main() {
    fmt.Println("here we go...")
    program := "python"
    arg0 := "-c"
    arg1 := fmt.Sprintf("'%s'", "import pythonfile; print pythonfile.cat_strings(\"foo\", \"bar\")'")
    cmd := exec.Command(program, arg0, arg1)
    fmt.Println("command args:", cmd.Args)
    out, err := cmd.CombinedOutput()
    if err != nil {
        fmt.Println("Concatenation failed with error:", err.Error())
        return
    }
    fmt.Println("concatenation length:", len(out))
    fmt.Println("concatenation:", string(out))
    fmt.Println("...done")
}

Corresponding Python code:

def cat_strings(a, b):
    return a + b

Executing go run gofile yields:

here we go...
command args: [python -c 'import pythonfile; print pythonfile.cat_strings("foo", "bar")']
concatenation length:  0
concatenation:  
...done

The Solution

Overcoming this obstacle required the judicious removal of unnecessary quotes around the command itself:

package main

import (
    "fmt"
    "os/exec"
)

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

This modification resulted in a successful retrieval of the function's return value:

$ python -c "import pythonfile; print pythonfile.cat_strings('foo', 'bar')"
foobar

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