Persistent Python lists and dictionaries in MongoDB.
First, create/access your MongoDB collection using pymongo. If you are unfamiliar with pymongo, here are the quickstart docs!
from pymongo import MongoClient
client = MongoClient(
host='localhost',
port=27017,
username='user',
password='pass',
authSource='admin',
)
database = client["your_database_name"]
collection = database["your_collection_name"]
Then you can create dictionaries or lists that are backed by MongoDB!
MongoDict supports nearly all dictionary functions, like .keys(), .values(), .items(), .get(), .update(), .clear(), .copy(), and .popitem(). I believe .fromkeys() and .setdefault() are the only ones that don't work.
from mongoshelve import MongoDict
my_dict = MongoDict(
collection=collection,
name="my_dict",
) #creates an empty dict
Nested dictionaries and lists are also supported!
my_dict["first_entry"] = "hello world"
my_dict["second_entry"] = [1,2,3]
my_dict["third_entry"] = {"a": 1, "b": {"hi":"bye"}, "c": [1,2,3]}
Lists are fully supported except for one limitation. MongoList cannot store iterable values (ie [1,[1,2]] would not be supported as the second value is an iterable). This limitation arises because indexing specific array elements in MongoDB is tricky. If this is critical to your use case, please submit an issue!
from mongoshelve import MongoList
my_list = MongoList(
collection=collection,
name="my_list",
) #creates an empty list
my_list.append(1)
my_list.pop()
Both MongoList and MongoDict have an optional default_value parameter that can be used to set initial value of the list or dict in the MongoDB document. If default_value is not specified (default), the list or dict will be empty.
When MongoList/MongoDict is instantiated, it will check if the document exists in the MongoDB collection. If a document by this name already exists, the stored values will not be changed. If the document does not exist, it will be created using the default_value as the value.
If you want to overwrite the values using your default, you can run the following method:
from mongoshelve import MongoList
my_list = MongoList(
collection=collection,
name="my_list",
default_value=[1,2,3],
) # if document already exists, this will not overwrite the values
my_list.apply_default_values(overwrite=True) # this will overwrite the values