How Can I Successfully Retrieve Return Values from Python Functions Called Within a Go Program?

Calling Python Functions from Go and Retrieving Return Values

In scenarios where you need to leverage Python utilities within your Go programs, this guide will assist you in invoking Python functions and retrieving their return values.

The original code, as provided in the question:

package main

import "os/exec"
import "fmt"

func main() {
     fmt.Println("here we go...")
     program := "python"
     arg0 := "-c"
     arg1 := fmt.Sprintf("'import pythonfile; print pythonfile.cat_strings(\"%s\", \"%s\")'", "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("concatentation length: ", len(out))
     fmt.Println("concatenation: ", string(out))
     fmt.Println("...done")
}

Unfortunately, this code resulted in an empty return value. The solution lies in removing the enclosing apostrophes from the Python command:

package main

import "fmt"
import "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 alteration uncovers an interesting detail about Windows' EscapeArg function, which rewrites command line arguments by doubling backslashes before double quotes and escaping double quotes themselves. Thus, the original code was essentially escaping the Python command instead of executing it properly. By eliminating the enclosing apostrophes, the correct command is passed to Python and the function's return value is retrieved successfully.

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