GoPyLink

A lightweight Python & Go cross-language call framework for in-process communication.

Features

• Python Call Go - Python call Go functions, create Go type instances and invoke methods
• Go Call Python - Go call Python functions, create Python class instances and invoke methods
• Simple API - Minimal setup with intuitive interfaces

Limitations

GoPyLink is designed for data exchange only. All function parameters and return values must be plain data types (primitives, collections, structs with all fields public).

Channels, goroutines, functions and interface types (except any) are not supported as parameters or return values.

Installation

Go

go get github.com/ray4go/go-ray/gopylink

Python

pip install gopylink

Requires: Go 1.21+, Python 3.7+

# Ubuntu/Debian
sudo apt install build-essential

# CentOS/RHEL
sudo yum groupinstall "Development Tools"

# macOS
xcode-select --install

Python calling Go

1. Export Go Functions/Types

Create a lib.go file:

package main

import "github.com/ray4go/gopylink"

// Functions to export - all exported methods become callable from Python
type Functions struct{}

func (Functions) Hello(name string) string {
	return "Hello " + name
}

func (Functions) Add(a, b int) int {
	return a + b
}

// Classes to export - each method creates a new instance
type Classes struct{}

type Counter struct {
	value int
}

func (Classes) Counter(initial int) *Counter {
	return &Counter{value: initial}
}

func (c *Counter) Incr(n int) int {
	c.value += n
	return c.value
}

func (c *Counter) Value() int {
	return c.value
}

func init() {
	gopylink.Init(Functions{}, Classes{})
}

func main() {}

2. Build Go Shared Library

go build -buildmode=c-shared -o go.lib .

3. Call Go from Python

# main.py
import gopylink

# Load the Go library
lib = gopylink.load_go_lib("go.lib")

# Call Go functions
result = lib.func_call("Hello", "World")
print(result)  # Output: Hello World

result = lib.func_call("Add", 10, 20)
print(result)  # Output: 30

# Create Go type instance and call methods
counter = lib.new_type("Counter", 0)
print(counter.Incr(5))  # Output: 5
print(counter.Incr(3))  # Output: 8
print(counter.Value())  # Output: 8

Run the python script:

python main.py

Go calling Python

1. Export Python Functions/Classes

# main.py
import gopylink

@gopylink.export
def greet(name: str) -> str:
    return f"Hi, {name}!"

@gopylink.export
def multiply(a, b):
    return a * b

@gopylink.export
class Counter:
    def __init__(self, initial=0):
        self.value = initial

    def incr(self, n):
        self.value += n
        return self.value

if __name__ == "__main__":
    lib = gopylink.load_go_lib("go.lib")
    lib.func_call("Start")  # Start the Go logic

2. Call Python from Go

package main

import (
	"fmt"
	"github.com/ray4go/gopylink"
)

type functions struct{}

func (functions) Start() {
	// Call Python function
	result := gopylink.PythonFuncCall("greet", "Gopher")
	val, err := result.Get()
	fmt.Printf("greet: %v, err: %v\n", val, err) // Output: greet: Hello, Gopher!, err: <nil>

	// Call with typed result
	result = gopylink.PythonFuncCall("multiply", 6, 7)
	product, err := gopylink.Get[int](result)
	fmt.Printf("multiply: %v, err: %v\n", product, err) // Output: multiply: 42, err: <nil>

	// Create Python class instance
	cnt := gopylink.NewPythonClassInstance("Counter", 10)
	defer cnt.Close()

	res := cnt.MethodCall("incr", 5)
	val, err = res.Get()
	fmt.Printf("Counter.incr: %v, err: %v\n", val, err) // Output: Counter.incr: 15, err: <nil>
}

func init() {
	gopylink.Init(functions{}, nil)
}

func main() {}

3. Build and Run

go build -buildmode=c-shared -o go.lib .
python main.py

Note that when calling Python from Go, the entry point remains the Python script. The Go shared library is loaded into the Python process, which then starts the Go logic.

API Reference

Python API

Go API

See Go API Reference for more details.

Type Conversion

Types are automatically converted via msgpack:

For detailed type conversion rules, see the Cross-Language Type Conversion Guide.

Thread Safety

GoPyLink operations are thread-safe. Multiple goroutines/threads can safely call cross-language functions concurrently.

Performance Notes

Go FFI has approximately 30ns overhead per call compared to native C/C++ FFI due to Go's virtual stack. This overhead is:

• Negligible for coarse-grained operations
• Significant for micro-calls requiring millions of invocations per second

Best Practices

Golang Parameter and return types

• Prefer concrete types (primitive types, composites, structs, and their pointers) over interface types for parameters
• Do not use interface types as return values except for any type.

Golang Error handling

Do not return error (as it is an interface) directly from Ray Task functon / Actor methods. Instead, return concrete types to indicate errors (e.g., return int for error code), or just panic in your code.

When ObjectRef.GetAll() / ObjectRef.Getinto() / ray.GetN(obj) is called on a panic-ed task/actor, it will return an error. You can use fmt.Printf("%+v", err) to print the error stack trace.

License

MIT