goinpy 0.4

Use Golang functions inside Python code

goinpy - Golang In Python

This is a python package, which is made to use Golang functions inside Python code more easily.

Embedding Golang functions in python can be very handy, for example, if you want to move some big computations from slow Python to faster Golang and immediately get a result back.

For now (and probably ever), Golang and Python full function embedding can't be implemented due languages nature, see issue #6. You can use this package for simple examples, but for advanced stuff, try something else (for example, Python requests with Golang localhost "net/http" listener).

Source code is in goinpy/goinpy.py.

Installation

You can install this package from PyPi with pip install goinpy;

Then in python code, import it with from goinpy import *.

How to use

Most of these examples are represented in the examples/ folder.

Basic "Hello World!" example

Golang function export

Let's start with exporting a simple Golang "Hello World!" function.

package main

import (
    "C"
    "fmt"
)

//export TestFunc
func TestFunc() {
    fmt.Println("Hello World!")
}

func main() {

}

To export functions, we need to import "C" library, and specify by //export NAME comment, what function we need to export. Also make sure func main() {} is exists.

Compiling to C

After we made the Golang file, for example, HelloWorld.go, we need to compile it to C. We can do it by typing go build -o HelloWorld.so -buildmode=c-shared HelloWorld.go in terminal. This command is also represented in example/golangCode.go.

If all is okay, we should now see three different files: HelloWorld.go, HelloWorld.so, HelloWorld.h. .so is the compiled file that we need.

Call Golang function from Python

Let's create HelloWorld.py.

from goinpy import *

golangLib = load_go_lib('HelloWorld.so')

golangLib.TestFunc()

Here we just imported all from goinpy package, loaded compiled C library into golangLib, and called TestFunc function with it.

After running python HelloWorld.py in a terminal, the output should be Hello World! as expected.

Advanced examples with different types

Integer example

golangCode.go:

//export TestInt
func TestInt(x, y int) int {
    return x + y
}

pythonCode.py:

setup_go_func(golangLib.TestInt, [intGo, intGo], intGo)
input_1 = intGo(5)
input_2 = intGo(10)
output_result = golangLib.TestInt(input_1, input_2)  # 15

Here we met 2 new functions:

• intGo(int) - convert python int to golang int. You can convert it back by some_int.value;
• setup_go_func(func, arg_types=None, res_type=None) - if Golang function is taking or returning some data, we need to setup this function. First func arg is the function we are trying to setup. Second arg_types arg is a list for types this function is waiting. Third res_type arg is a type it's returning. Also it returns func arg back for cases when you want to setup function and assign it to variable in one line.

Float example

golangCode.go:

//export TestFloat
func TestFloat(x float64) float64 {
    return x / 2
}

pythonCode.py:

setup_go_func(golangLib.TestFloat, [floatGo], floatGo)
input_data = floatGo(12.2)
output_result = golangLib.TestFloat(input_data)  # 6.1

Here we met 1 new function:

• floatGo(float) - convert python float to golang float64.

String example

golangCode.go:

//export TestString
func TestString(x *C.char) *C.char {
    str := C.GoString(x)
    newStringC := C.CString("Hello, " + str)
    return newStringC
}

Note that for strings, we need to use *C.char for in and out. You can convert between this and normal string by using C.GoString(char) and C.CString(string).

pythonCode.py:

setup_go_func(golangLib.TestString, [stringGo], stringGo)
input_data = str_to_go('World')
output_result = str_to_py(golangLib.TestString(input_data))  # "Hello, World!"

Here we met 3 new functions:

• stringGo - golang string;
• str_to_go(str) - convert python str to golang string;
• str_to_py(string) - convert golang string to python str.

Slice example

golangCode.go:

//export TestSlice
func TestSlice(x []int) []int {
    x[0] = 666
    return x
}

pythonCode.py:

setup_go_func(golangLib.TestSlice, [intGoSlice], intGoSlice)
input_list = [intGo(123), intGo(456)]
input_data = list_to_slice(input_list, intGo)
output_result = slice_to_list(golangLib.TestSlice(input_data))  # [666, 456]

Here we met 3 new functions:

• intGoSlice - golang []int slice. There is also floatGoSlice, stringGoSlice and boolGoSlice;
• list_to_slice(list, data_type: None) - convert python list to golang slice. First arg is actual list we are converting. Second additional data_type arg is what type this slice is storing (NOTE THAT SLICE CAN'T STORE DIFFERENT FILE TYPES AT ONCE).
• slice_to_list(slc) - convert golang slice to python list.

Bool example

golangCode.go:

//export TestBool
func TestBool(x bool) bool {
    return !(x)
}

pythonCode.py:

setup_go_func(golangLib.TestBool, [boolGo], boolGo)
input_data = False
output_result = golangLib.TestBool(input_data)  # True

Here we met 1 new function:

• boolGo - golang bool. No need in converting python bool to golang bool;

Notes

• If multiple .so libraries is imported, make sure they are compiled under different names;
• Generated .so file will only work on the same system. For example, if it's generated on Windows (like in this repo), it will not work on Linux or Mac;
• You can't create slices inside slices (issue #3);
• Supported types are: int, float64, string, bool and slice containing any of previous 4 types;
• Golang function can't return more than 1 variable to python.
• In case of any weird error, see issue #6.

Other

CHANGELOG

LICENSE