Is there a python function to return a new dict with a new key added, like assoc in clojure?

Question

I'm writing python after writing clojure for a while, and I'm a little rusty, but I am approaching it in a much more functional style. To follow a pattern I used in clojure, I want to use map (or list comprehension) with something like assoc to set keys in each dict in a list.

I have a list of records, and I want to restructure them with list comprehensions.

The record looks like this:

{
  "timestamp":1232435235315,
  "data": {
    "foo": 2345,
    "bar": 1454
  }
}

I want to get a dict containing the timestamp and the keys from data.

newlist = [ assoc(x, "timestamp", x["timestamp"]) for x in mylist ]

I could implement an assoc pretty easily, but I'd like for it to exist already in a library:

def assoc(coll, k, v):
  newcoll = coll.copy()
  newcoll[k] = v
  return newcoll  

Does anyone out there know a library which already contains something like this or a pythonic way to do it concisely without mutating the original list?

Answer 1

Sure, you can simply use dict(), for example:

old = {"a": 1}
new_one = dict(old, new_key=value)
#or
new_one = dict(old, {...})