from runtime_context import RuntimeContextWrapper

runtime_context = RuntimeContextWrapper()


def do_something(i):
    if runtime_context.dry_run:
        print('{} - dry run'.format(i))
    else:
        print('{} - for real'.format(i))


with runtime_context(dry_run=False):
    do_something(1)  # for real

    with runtime_context(dry_run=True):
        do_something(2)  # dry run

        runtime_context.dry_run = False
        do_something(3)  # for real

    with runtime_context():
        do_something(4)  # for real

        runtime_context.dry_run = True
        do_something(5)  # dry run

    do_something(6)  # for real

import json
from typing import Union  # noqa

from runtime_context import EnvBase, runtime_context_env  # noqa


@runtime_context_env
class YourApp:
    dry_run = False
    db_name = None
    config_file = None


env = YourApp()  # type: Union[YourApp, EnvBase]


@env.context_var_set.listener(predicate=lambda name: name == 'config_file')
def reload_config():
    if not env.config_file:
        return

    print('Reloading config from {}'.format(env.config_file))
    with open(env.config_file) as f:
        config = json.load(f)
        for k, v in config.items():
            env.set(k, v)


with env():
    assert env.dry_run is False
    assert env.db_name is None

    env.config_file = 'config.json'  # prints 'Reloading config from config.json'

    assert env.db_name == 'products'  # read from config.json file

    with env(dry_run=True):
        assert env.dry_run is True