更新列表，该列表是字典中键的值

Question

I have a dictionary like:

d = {c1: l1, c2: l2, c3: l3, ......., cn: ln}

where c1, c2,.... cn are strings and l1, l2,... l3 are lists.

Now, I have a function where the list needs to be updated, for a pair of variables c, x:

1. if c is in d:

Find the (key, value) for c, and update the corresponding l with x

2. if c not in d:

Create a cm: lm pair in d

So far, what I've tried is:

if c in d:
    d.update({cn:ln.append(x)})
else:
    d.update({cm:lm.insert(x)})

But the code isn't working as expected.

Any pointers as to why the code not working would be helpful, and any suggestions for the code which can make it work are welcome.

PS: The c and x values are passed as arguments to a function, where all the updating happens.

For clarification, I'm running Python 2.7, on PyCharm, on Windows 10.

Edit:

Answer 1

if c in d:
    # d[c] corresponds to the list you want to update
    d[c].append(x)
    # the append function directly modifies the list at d[c], 
    # so we don't have to do any re-assignment
else:
    # d[c] does not exist, so we create a new list with your item
    d[c] = [x]

Answer 2

Please see https://repl.it/repls/ExternalCornyOpendoc Example code as below:

d = {
  "Key1":[1,2,3],
  "Key2":[11,12,13]
}

def test(c, x):
  if c in d:
    d[c].append(x);
  else:
    d[c] = [x];
  print(d)

test("Key1", 12)
test("Key3", 122)