Erlastic
========
Usage
-----
Erlastic allows you to serialize/deserialize python objects into `erlang
binary term <http://erlang.org/doc/apps/erts/erl_ext_dist.html>`__.
Basic usage is :
::
import erlastic
py_struct = erlastic.decode(binary_term)
binary = erlastic.encode(py_struct)
Erlang Port communication usage
-------------------------------
The library contains also a function to use python with erlastic in an
erlang port to communicate erlang binary term : ``port_communication()``
which return ``(mailbox,port)``. They are both python coroutines
(executed generator) so you can communicate with erlang coroutine using
python abstractions :
- ``mailbox`` waits for port message in stdin, iterating over messages
decoded from binary erlang term format.
- ``port`` waits for ``send(python_struct)``
(http://docs.python.org/3.3/reference/expressions.html#generator.send)
then encode ``python_struct`` into binary term format and send it to
the erlang port via stdout.
So for instance, if you want to create a Python server which receives
the tuple {A,B} and return {ok,A/B} of {error,divisionbyzero} you can
use at the python side :
::
from erlastic import port_connection,Atom as A
mailbox,port = port_connection()
for (a,b) in mailbox:
port.send((A("ok"),a/b) if b!=0 else (A("error"),A("divisionbyzero")))
and at the erlang side, use ``-u`` python parameter to prevent python
output buffering, use 4 bytes packet length because it is the
configuration used by the python generators.
::
Port = open_port({spawn,"python3 -u add_server.py"},[binary,{packet,4}]),
Div = fun(A,B)->
Port ! {self(),{command,term_to_binary({A,B})}},
receive {Port,{data,Bin}}->binary_to_term(Bin) after 1000->{error,timeout} end
end,
io:format("send {A,B}=~p, python result : ~p~n",[{32,10},Div(32,10)]),
io:format("send {A,B}=~p, python result : ~p~n",[{2,0},Div(2,0)]),
io:format("send {A,B}=~p, python result : ~p~n",[{1,1},Div(1,1)])
or in elixir :
::
port = Port.open({:spawn,'python3 -u add_server.py'},[:binary|[packet: 4]])
div = fn(a,b)->
port <- {self,{:command,term_to_binary({a,b})}}
receive do {_,{:data,b}} -> binary_to_term(b) after 100->{:error,:timeout} end
end
IO.puts "send {a,b}={32,10}, python result : #{inspect div.(32,10)}"
IO.puts "send {a,b}={2,0}, python result : #{inspect div.(2,0)}"
IO.puts "send {a,b}={1,1}, python result : #{inspect div.(1,1)}"