registration.py

import importlib

# Default Config
DEFAULT_CONFIG = {
        'allow_step_back': False,
        'seed': None,
        }

class EnvSpec(object):
    ''' A specification for a particular instance of the environment.
    '''

    def __init__(self, env_id, entry_point=None):
        ''' Initilize

        Args:
            env_id (string): The name of the environent
            entry_point (string): A string the indicates the location of the envronment class
        '''
        self.env_id = env_id
        mod_name, class_name = entry_point.split(':')
        self._entry_point = getattr(importlib.import_module(mod_name), class_name)

    def make(self, config=DEFAULT_CONFIG):
        ''' Instantiates an instance of the environment

        Returns:
            env (Env): An instance of the environemnt
            config (dict): A dictionary of the environment settings
        '''
        env = self._entry_point(config)
        return env

class EnvRegistry(object):
    ''' Register an environment (game) by ID
    '''

    def __init__(self):
        ''' Initilize
        '''
        self.env_specs = {}

    def register(self, env_id, entry_point):
        ''' Register an environment

        Args:
            env_id (string): The name of the environent
            entry_point (string): A string the indicates the location of the envronment class
        '''
        if env_id in self.env_specs:
            raise ValueError('Cannot re-register env_id: {}'.format(env_id))
        self.env_specs[env_id] = EnvSpec(env_id, entry_point)

    def make(self, env_id, config=DEFAULT_CONFIG):
        ''' Create and environment instance

        Args:
            env_id (string): The name of the environment
            config (dict): A dictionary of the environment settings
        '''
        if env_id not in self.env_specs:
            raise ValueError('Cannot find env_id: {}'.format(env_id))
        return self.env_specs[env_id].make(config)

# Have a global registry
registry = EnvRegistry()

def register(env_id, entry_point):
    ''' Register an environment

    Args:
        env_id (string): The name of the environent
        entry_point (string): A string the indicates the location of the envronment class
    '''
    return registry.register(env_id, entry_point)

def make(env_id, config={}):
    ''' Create and environment instance

    Args:
        env_id (string): The name of the environment
        config (dict): A dictionary of the environment settings
        env_num (int): The number of environments
    '''
    _config = DEFAULT_CONFIG.copy()
    for key in config:
        _config[key] = config[key]

    return registry.make(env_id, _config)