go_python.slide

# Calling Go from Python

Pavel Tišnovský
https://github.com/RedHatOfficial/GoCourse

## Go + Python

.image ./common/golang.png
.image ./common/python.png

## Two different worlds

* Python has support for FFI, cffi, ctypes etc.
* It is possible to compile Go library to .so/.dll
   - integration seems easy
* But
   - in fact the integration is based on common ground: C
   - different data types
   - totally different data structures
   - GC on both sides! (different ones)
* Let's try more convenient approaches first

## Step #1: how to integrate Go with C

* Go library with exported function
* Compilation into shared library (DLL, so)
* Loading library into C

## Go library

.code go_python/example1.go

## Compile and build a library

```
go build -buildmode=c-shared so1.go
```

## Loading Go library from C (1/2)

.code go_python/example1A.c

## Loading Go library from C (2/2)

.code go_python/example1B.c


* Compile and build

```
gcc -ansi use_so1.c -ldl
```

## Step 2: now use Python instead of C

## System-wide library (or LD_LIBRARY_PATH)

.code go_python/example1A.py

## Local library

.code go_python/example1B.py

## `main` and `init` functions possible

.code go_python/example2.go

## Go function with parameters and return value

.code go_python/example3.go

## Call from Python

.code go_python/example3A.py

## Common problems

.code go_python/example3B.py

.code go_python/example3C.py

## System-independent data types

.code go_python/example4.go

## Python side

.code go_python/example4A.py

## Max vals

.code go_python/example4B.py

.code go_python/example4C.py

## Passing strings to Go

.code go_python/example5.go

## Strings on Python side

.code go_python/example5.py

## Type `*C.char`

.code go_python/example6.go

## Strings on Python side

.code go_python/example6A.py

.code go_python/example6B.py

.code go_python/example6C.py