23 – Chain multiple dictionaries

23 – Chain multiple dictionaries#

You can use the object ChainMap from the module collections to create a unified view over a hierarchy of dictionaries. The ChainMap object accesses the underlying dictionaries in order, stopping once it finds the key you are looking for:

from collections import ChainMap

default = {
    "user": "user",
    "theme": "light",
    "lan": "en",
}

local = {
    "theme": "dark",
}

user = {
    "user": "rodrigo",
}

settings = ChainMap(user, local, default)

print(settings["user"])  # rodrigo
print(settings["theme"])  # dark
print(settings["lan"])  # en

The underlying dictionaries can still be modified and the changes are reflected in the chained view:

user["lan"] = "pt"
print(settings["lan"])  # pt