gistfile1.txt

foo = {
    'nested': {
        'dict': 42
    }
}

query = 'nested.dict'

# reduce:
from functools import reduce
value = reduce(lambda accu, key: accu[key], query.split('.'), foo)

assert(value == 42)

# ???:
accu = foo
for key in query.split('.'):
    accu = accu[key]

assert(accu == 42)