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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"mongoengine.connection.ConnectionError: Cannot connect to database default","articleBody":"I got this error when running run.py\n\n```\n(flask-example) C:\\Users\\David\\python-ninja\\flask-example\u003epython run.py\nTraceback (most recent call last):\n  File \"run.py\", line 4, in \u003cmodule\u003e\n    app = create_app('settings')\n  File \"C:\\Users\\David\\python-ninja\\flask-example\\application.py\", line 20, in create_app\n    db.init_app(app)\n  File \"c:\\Users\\David\\python-ninja\\flask-example\\lib\\site-packages\\flask_mongoengine\\__init__.py\", line 66, in init_app\n    self.connection = mongoengine.connect(**conn_settings)\n  File \"c:\\Users\\David\\python-ninja\\flask-example\\lib\\site-packages\\mongoengine\\connection.py\", line 164, in connect\n    return get_connection(alias)\n  File \"c:\\Users\\David\\python-ninja\\flask-example\\lib\\site-packages\\mongoengine\\connection.py\", line 126, in get_connection\n    raise ConnectionError(\"Cannot connect to database %s :\\n%s\" % (alias, e))\nmongoengine.connection.ConnectionError: Cannot connect to database default :\nFalse is not a read preference.\n```\n\nI fixed it by adding to settings.py\n\n```\nfrom pymongo import read_preferences\n```\n\nand\n\n```\n'read_preference': read_preferences.ReadPreference.PRIMARY\n```\n\nto MONGODB_SETTINGS.\n","author":{"url":"https://github.com/dvdme","@type":"Person","name":"dvdme"},"datePublished":"2015-04-12T02:11:33.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/2/flask-example/issues/2"}