Singleton sandbox

main.py

import logging
import types
from modules import module_helloworld

#####################################
# Bad
# from proxy_lib import ProxySingleton

# Good
from proxies.proxy_lib import ProxySingleton, get_modules, get_path, get_fake_module
#####################################

FORMAT = '[%(filename)20s] %(funcName)18s : %(message)s'
logging.basicConfig(format=FORMAT)
_logger = logging.getLogger(__name__)
_logger.setLevel(logging.INFO)


def start_execution():
    ProxySingleton.action(data=1)
    hello_world = module_helloworld.get_helloworld()
    _logger.info(hello_world)


if __name__ == "__main__":
    _logger.info("Modules:\n\t{}".format("\n\t".join(get_modules())))
    _logger.info("Path:\n\t{}".format("\n\t".join(get_path())))
    _logger.info("-"*30)

    _logger.info("Starting execution")
    ProxySingleton.setup(parameter=123)
    start_execution()

module_helloworld.py

from proxies.proxy_lib import ProxySingleton
import sys
import logging
_logger = logging.getLogger(__name__)
_logger.setLevel(logging.INFO)

sys.path.insert(0, "proxies")

def get_helloworld():
    _logger.info("Triggering Hello World")
    ProxySingleton.action(data=2)
    return "Hello world!"

proxy_lib.py

from sys import modules, path
import types
import logging
_logger = logging.getLogger(__name__)
_logger.setLevel(logging.INFO)


def get_modules(name="proxy_lib"):
    result = []
    for module_name in modules.keys():
        if name.lower() in module_name.lower():
            result.append("\t> {:20} : {}".format(module_name, modules[module_name]))
    return result


def get_path():
    result = []
    for dir in path:
        if dir.startswith("/usr"):
            continue
        result.append("\t- {}".format(dir))
    return result


class ProxySingleton(object):
    activated = False
    parameter = None

    @classmethod
    def setup(cls, parameter):
        cls.parameter = parameter
        cls.activated = True
        _logger.info("[ID:{}] Proxy service activated".format(id(cls)))

    @classmethod
    def action(cls, data):
        if not cls.activated:
            _logger.info("[ID:{}] Proxy is not activated. Skipping".format(id(cls)))
            return
        old_parameter = cls.parameter
        cls.parameter = data
        new_parameter = cls.parameter
        _logger.info("[ID:{}] Successfully executed action. Changed parameter from {} to {}".format(
            id(cls),
            old_parameter,
            new_parameter
        ))