Erlang port protocol
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Description
The erlport Python library implements Erlang external term format and Erlang port protocol for easier integration of Python and Erlang.
The library exports the following classes and functions:
- Port(packet=1, use_stdio=False, compressed=False) - class implementing port which connects with the corresponding Erlang port. See open_port/2 for description of packet and use_stdio arguments. compressed is the zlib compression level or True for the default of 6.
- Protocol() - class which simplifies creation of request-response protocols.
- Atom(str) - class which represents an Erlang atom.
- String(unicode | list) - class representing an Erlang string. Must be used as a wrapper if Unicode string expected instead of a list.
- BitBinary(str) - class representing an Erlang bitstring whose length in bits is not a multiple of 8.
- decode(str) - function to convert binary data into a term.
- encode(term, compressed=False) - function to convert a term into the external format. compressed is the zlib compression level or True for the default of 6.
- IncompleteData - exception raised by decode() in case of incomplete input data.
Installation
Prerequisites:
- Erlang >= R11B-4
- Python >= 2.4
To install the library use easy_install from setuptools package like this:
$ easy_install erlport
Examples
See examples directory in the source distribution for additional examples.
For simple request-response protocol use Port and Protocol on the Python side like this:
from erlport import Port, Protocol class HelloProtocol(Protocol): def handle_hello(self, name): return "Hello, %s" % name if __name__ == "__main__": proto = HelloProtocol() proto.run(Port(use_stdio=True))
On the Erlang side function hello() can be called like this:
-module(hello). -export([hello/1]). hello(Name) -> Port = open_port({spawn, "python -u hello.py"}, [{packet, 1}, binary]), port_command(Port, term_to_binary({hello, Name})), receive {Port, {data, Data}} -> binary_to_term(Data) end.
Test it in the Erlang shell:
1> c(hello). {ok,hello} 2> hello:hello("Bob"). "Hello, Bob"
Notes for Windows users
- It seems Erlang’s open_port function ignores nouse_stdio option on Windows. So the Port class must be instantiated with use_stdio=True argument.
- Python must be ran with -u option to open stdin/stdout in binary mode.
Feedback
Please report bugs, offer suggestions or feedback at:
- Report bugs at http://github.com/hdima/erlport/issues
- Email me at <dima at hlabs.org>
- Write or follow me at http://twitter.com/hdima
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