python - 如何根据环境从我的 settings.py DATABASES 数组中激活数据库设置？

Question

我将 Django 与 Python 3.7 结合使用。我有一个 settings.py 文件，其中包含一些数据库设置 ...

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'mainpage',
        'USER': 'mainpage',
        'PASSWORD': 'password',
        'HOST': 'localhost',
        'PORT': '5432'
    },
    'production': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'mainpage',
        'USER': 'mainpage',
        'PASSWORD': 'password',
        'HOST': 'localhost',
        'PORT': '5432'
    }
}

该文件包含许多其他内容，但我在这里只包含了数据库数组。是否可以根据我的环境或环境变量从我的阵列中激活特定的数据库配置？我不希望有多个设置文件，因为这样我就必须在其中重复很多不会在环境中改变的其他配置。如果需要的话，我很乐意将数据库设置移动到它们自己的文件中，但我不确定它们将如何被激活。

编辑:根据 Scott Skiles 的回答，这是我在删除 settings.py 并添加其他目录和文件时遇到的错误，但在加载 Python 控制台时遇到此错误...

  File "/Users/davea/Documents/workspace/mainpage_project/venv/lib/python3.7/site-packages/django/__init__.py", line 19, in setup
    configure_logging(settings.LOGGING_CONFIG, settings.LOGGING)
  File "/Users/davea/Documents/workspace/mainpage_project/venv/lib/python3.7/site-packages/django/conf/__init__.py", line 57, in __getattr__
    self._setup(name)
  File "/Users/davea/Documents/workspace/mainpage_project/venv/lib/python3.7/site-packages/django/conf/__init__.py", line 42, in _setup
    % (desc, ENVIRONMENT_VARIABLE))
django.core.exceptions.ImproperlyConfigured: Requested setting LOGGING_CONFIG, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.

这是我的init.py 文件。自项目创建以来我没有改变它......

"""
Settings and configuration for Django.

Read values from the module specified by the DJANGO_SETTINGS_MODULE environment
variable, and then from django.conf.global_settings; see the global_settings.py
for a list of all possible variables.
"""

import importlib
import os
import time
import warnings
from pathlib import Path

from django.conf import global_settings
from django.core.exceptions import ImproperlyConfigured
from django.utils.deprecation import RemovedInDjango30Warning
from django.utils.functional import LazyObject, empty

ENVIRONMENT_VARIABLE = "DJANGO_SETTINGS_MODULE"


class LazySettings(LazyObject):
    """
    A lazy proxy for either global Django settings or a custom settings object.
    The user can manually configure settings prior to using them. Otherwise,
    Django uses the settings module pointed to by DJANGO_SETTINGS_MODULE.
    """
    def _setup(self, name=None):
        """
        Load the settings module pointed to by the environment variable. This
        is used the first time settings are needed, if the user hasn't
        configured settings manually.
        """
        settings_module = os.environ.get(ENVIRONMENT_VARIABLE)
        if not settings_module:
            desc = ("setting %s" % name) if name else "settings"
            raise ImproperlyConfigured(
                "Requested %s, but settings are not configured. "
                "You must either define the environment variable %s "
                "or call settings.configure() before accessing settings."
                % (desc, ENVIRONMENT_VARIABLE))

        self._wrapped = Settings(settings_module)

    def __repr__(self):
        # Hardcode the class name as otherwise it yields 'Settings'.
        if self._wrapped is empty:
            return '<LazySettings [Unevaluated]>'
        return '<LazySettings "%(settings_module)s">' % {
            'settings_module': self._wrapped.SETTINGS_MODULE,
        }

    def __getattr__(self, name):
        """Return the value of a setting and cache it in self.__dict__."""
        if self._wrapped is empty:
            self._setup(name)
        val = getattr(self._wrapped, name)
        self.__dict__[name] = val
        return val

    def __setattr__(self, name, value):
        """
        Set the value of setting. Clear all cached values if _wrapped changes
        (@override_settings does this) or clear single values when set.
        """
        if name == '_wrapped':
            self.__dict__.clear()
        else:
            self.__dict__.pop(name, None)
        super().__setattr__(name, value)

    def __delattr__(self, name):
        """Delete a setting and clear it from cache if needed."""
        super().__delattr__(name)
        self.__dict__.pop(name, None)

    def configure(self, default_settings=global_settings, **options):
        """
        Called to manually configure the settings. The 'default_settings'
        parameter sets where to retrieve any unspecified values from (its
        argument must support attribute access (__getattr__)).
        """
        if self._wrapped is not empty:
            raise RuntimeError('Settings already configured.')
        holder = UserSettingsHolder(default_settings)
        for name, value in options.items():
            setattr(holder, name, value)
        self._wrapped = holder

    @property
    def configured(self):
        """Return True if the settings have already been configured."""
        return self._wrapped is not empty


class Settings:
    def __init__(self, settings_module):
        # update this dict from global settings (but only for ALL_CAPS settings)
        for setting in dir(global_settings):
            if setting.isupper():
                setattr(self, setting, getattr(global_settings, setting))

        # store the settings module in case someone later cares
        self.SETTINGS_MODULE = settings_module

        mod = importlib.import_module(self.SETTINGS_MODULE)

        tuple_settings = (
            "INSTALLED_APPS",
            "TEMPLATE_DIRS",
            "LOCALE_PATHS",
        )
        self._explicit_settings = set()
        for setting in dir(mod):
            if setting.isupper():
                setting_value = getattr(mod, setting)

                if (setting in tuple_settings and
                        not isinstance(setting_value, (list, tuple))):
                    raise ImproperlyConfigured("The %s setting must be a list or a tuple. " % setting)
                setattr(self, setting, setting_value)
                self._explicit_settings.add(setting)

        if not self.SECRET_KEY:
            raise ImproperlyConfigured("The SECRET_KEY setting must not be empty.")

        if self.is_overridden('DEFAULT_CONTENT_TYPE'):
            warnings.warn('The DEFAULT_CONTENT_TYPE setting is deprecated.', RemovedInDjango30Warning)

        if hasattr(time, 'tzset') and self.TIME_ZONE:
            # When we can, attempt to validate the timezone. If we can't find
            # this file, no check happens and it's harmless.
            zoneinfo_root = Path('/usr/share/zoneinfo')
            zone_info_file = zoneinfo_root.joinpath(*self.TIME_ZONE.split('/'))
            if zoneinfo_root.exists() and not zone_info_file.exists():
                raise ValueError("Incorrect timezone setting: %s" % self.TIME_ZONE)
            # Move the time zone info into os.environ. See ticket #2315 for why
            # we don't do this unconditionally (breaks Windows).
            os.environ['TZ'] = self.TIME_ZONE
            time.tzset()

    def is_overridden(self, setting):
        return setting in self._explicit_settings

    def __repr__(self):
        return '<%(cls)s "%(settings_module)s">' % {
            'cls': self.__class__.__name__,
            'settings_module': self.SETTINGS_MODULE,
        }


class UserSettingsHolder:
    """Holder for user configured settings."""
    # SETTINGS_MODULE doesn't make much sense in the manually configured
    # (standalone) case.
    SETTINGS_MODULE = None

    def __init__(self, default_settings):
        """
        Requests for configuration variables not in this class are satisfied
        from the module specified in default_settings (if possible).
        """
        self.__dict__['_deleted'] = set()
        self.default_settings = default_settings

    def __getattr__(self, name):
        if name in self._deleted:
            raise AttributeError
        return getattr(self.default_settings, name)

    def __setattr__(self, name, value):
        self._deleted.discard(name)
        if name == 'DEFAULT_CONTENT_TYPE':
            warnings.warn('The DEFAULT_CONTENT_TYPE setting is deprecated.', RemovedInDjango30Warning)
        super().__setattr__(name, value)

    def __delattr__(self, name):
        self._deleted.add(name)
        if hasattr(self, name):
            super().__delattr__(name)

    def __dir__(self):
        return sorted(
            s for s in list(self.__dict__) + dir(self.default_settings)
            if s not in self._deleted
        )

    def is_overridden(self, setting):
        deleted = (setting in self._deleted)
        set_locally = (setting in self.__dict__)
        set_on_default = getattr(self.default_settings, 'is_overridden', lambda s: False)(setting)
        return deleted or set_locally or set_on_default

    def __repr__(self):
        return '<%(cls)s>' % {
            'cls': self.__class__.__name__,
        }


settings = LazySettings()

Answer 1

我只使用一个环境变量和包 environ .

env = environ.Env()
if not env.bool('PRODUCTION', 'False'):
    # Select this PRODUCTTION=False or if not defined 
    DATABASES = 'default': {
        # ...
    }
else:
   DATABASES = 'default': {
       # ...
    }