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Easily create a CLI and JSON-RPC interface from a common API definition.

Project description

Easily create a CLI and JSON-RPC interface from a common API definition.


pip install apigen

Example API definition

I simple example application with an add command.

# from examples/
import apigen

# automatically added verison command will use module version if present
# rpc exceptions will also include module version if persent
__version__ = "1.0.0"

class Calculator(apigen.Definition):  # Programm name taken from class name.
    """Example Programm"""  # Programm help text taken from class doc string.

    def add(self, a, b):  # Command name and args taken from method.
        """adds two items"""  # Help text taken from method doc string.
        return a + b  # Returned rpc/cli output (must be JSON serializable).

if __name__ == "__main__":  # Run CLI interface.

The created CLI/RPC interface behaves as you would expect from a python class.

  • Programm arguments are taken from the __init__ method.

  • Command arguments are taken from the respective command methods.

  • Manditory and optional arguments work just like you would expect in python.

  • In addition arguments with the default value False are flags in the CLI.

# from examples/
import apigen

class ArgumentsExample(apigen.Definition):

    def __init__(self, quiet=False, config_path="default/path.json"):
        self.quiet = quiet
        self.config_path = config_path

    def show_args(self, first, second, optional="Default"):
        if not self.quiet:
        return { 'first': first, 'second': second, 'optional': optional }

if __name__ == "__main__":

Generated CLI interface (uses argparse)

Generated CLI interface.

# Program, command and arguments order.
$ python [program arguments] <command> [command arguments]

# Argument format.
$ python positional_argument_value --optional_argument=value --flag

Showing the generated help.

# Show programm help text.
$ python examples/ --help

# Show command help text
$ python examples/ startserver --help

CLI arguments must be given as json data.The json data automatically is unmarshalled before calling the command function and the returned result is automatically marshalled.

$ python examples/ add 1 2

$ python examples/ add 1.1 2.2

$ python examples/ add "foo" "bar"

$ python examples/ add "[1,2,3]" "[4,5,6]"

Client side json-rpc usage with python-jsonrpc.

Starting the jsonrpc server from the command line.

$ python examples/ startserver
Starting Calculator json-rpc service at http://localhost:8080

RPC arguments must be given as json serializable data. The arguments will automatically be marshalled and unmarshalled.

>>> import pyjsonrpc

>>> rpc = pyjsonrpc.HttpClient(url = "http://localhost:8080")

>>> rpc.add(1, 2)

>>> rpc.add(1.1, 2.2)

>>> rpc.add("foo", "bar")

>>> rpc.add([1,2,3], [4,5,6])
[1, 2, 3, 4, 5, 6]

Client side exception handeling.

# from examples/
import json
import pyjsonrpc

rpc = pyjsonrpc.HttpClient(url="http://localhost:8080")
    print rpc.add(1, "str")
except pyjsonrpc.rpcerror.JsonRpcError as e:
    print e.code  # see

    # Server error if an exception is raised during the call.
    if e.code <= -32000 and e.code >= -32099:
        print e.message  # source exception message
        data = json.loads(
        print data["classname"]  # source exception class name
        print data["repr"]  # source exception repr string
        print data["traceback"]  # source exception traceback
        print data["version"]  # source module version if present

Starting the jsonrpc service from within python.

import basic
api = basic.Calculator()

Getting a pyjsonrpc.HttpRequestHandler for further use.

import basic
api = basic.Calculator()

Client side json-rpc usage with javascript

// from examples/node.js

// npm install node-json-rpc
var rpc = require('node-json-rpc');

var client = new rpc.Client({
      port: 8080,
      host: '',
      path: '/',
    "jsonrpc": "2.0",
    "method": "add",
    "params": {
      a: 1,
      b: 3
    "id": 0
  function(err, res) {
    if (err) {
      console.log("Error add");
    } else {
      console.log("Success add");
$ node examples/node.js
Success add
{ jsonrpc: '2.0', id: 0, result: 4 }

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