When it comes to fault-tolerant systems, there are very few languages that can beat Erlang
. While Erlang
is a great language for building fault-tolerant systems, it is not the best language for building AI/ML applications. There are instances where you would want to use Python
for building AI/ML applications and Erlang
for building fault-tolerant systems. In such cases, you would want to use Erlang
and Python
together. This is where Erlport library comes in.
But before understanding Erlport, you need an understanding of ports
in Erlang.
Ports
In simple terms, ports
are used to communicate with external programs which are not written in Erlang. So if you have a C program or a Python program and you want to communicate with it from Erlang, you can use ports
. It's not a restriction that you can only use ports
to communicate with external programs, you can also use ports
to communicate with other Erlang nodes.Port
provides you with a byte-oriented interface. Which means, you send a list of bytes and receive a list of bytes during the communication. This also means you need to handle the encoding and decoding of the data at both ends by yourself.
Erlport
Erlport is a library that internally uses the port
mechanism for communication and provides a wrapper around it. This makes the integration of Erlang and Python very easy. Right now, Erlport supports Python and Ruby. In this article, we will be focusing on Erlang and Python implementation.
Installation
If you are using rebar3
for building your Erlang application, you can add the following dependency to your rebar.config
file.
...
{deps, [
erlport
]}.
...
Or you can use the GitHub link for the dependency.
{erl_opts, [debug_info]}.
{deps, [
{erlport, {git, "https://github.com/erlport/erlport.git", {tag, "v0.10.1"}}}
]}.
You'll also need to tell Erlang
to wait for the dependencies to be available before starting the app. This can be done by adding the entry in *.app.src
file.
{applications,
[kernel,
stdlib,
erlport
]},
Python program
Let's create an add
program in Python and keep the file in the priv
directory.
def add(a, b):
return a + b
Erlang program
The Erlang
program will initialize the Python port using python:start/1
function. And will call the add
function of the Python program using python:call/4
function. The python:call/4
function takes the Pid
of the Python port, the module name, the function name, and the list of arguments to be passed to the function.
Here, my Python
module is named, math
and the function is add
with 2
and 4
as parameters.
-module(main).
-export([call_python/0]).
call_python() ->
PythonCodePath = code:priv_dir(aiml_model_wrapper),
{ok, P} = python:start([{python_path, PythonCodePath}, {python, "python3"}]),
python:call(P, math, add, [2, 4]).
Running the program
Running the program is as simple as compiling and running the Erlang
program.
reabr3 compile
reabr3 shell
1> main:call_python().
Conclusion
In this article, we saw how we can use Erlang
and Python
together using Erlport
. This is a very simple example of how you can use Erlang
and Python
together. You can use this to build complex systems where you can use Erlang
for building fault-tolerant systems and Python
for building AI/ML applications. At GreyOrange I created an Erlang wrapper for our AI/ML models using the same approach.
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