For example I have a dictionary:
dictionary = {'dog' : 'bark', 'cat' : 'kitten'}
And I want to add another value 'woof' to the key 'dog' so that I get:
{'dog': ['bark','woof'], 'cat' : 'kitten'}
And then add another value 'speak' to the key 'dog' so that I get:
{'dog': ['bark','woof', 'speak'], 'cat' : 'kitten'}
etc.
Any help is appreciated.
You first need to convert the values associated with each key in your dict to lists: You can accomplish this via dict comprehension. Afterwards, it's simply a matter of appending items to the list at the desired key in the dictionary. The following code would work:
dictionary = {"dog" : "bark", "cat" : "kitten"}
dictionary = {key : [value] for key, value in dictionary.items()}
dictionary["dog"].append("woof")
dictionary["dog"].append("speak")
At which point, if you print dictionary, the output will be:
{'dog': ['bark', 'woof', 'speak'], 'cat': ['kitten']}
As far as I can tell, the solution is to initialize each dictionary value as a list from the start. For example, initialize your dictionary as dictionary = {'dog' : ['bark'], 'cat' : ['kitten']}. Then, when you want to add new values to your dictionary keys you can use dictionary["dog"].append("speak").
I would implement a defaultdict from the collections module.
Here is an example from the official docs:
>>> s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
>>> d = defaultdict(list)
>>> for k, v in s:
... d[k].append(v)
...
>>> sorted(d.items())
[('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])]
['dog']to see if its value is already a list (we know from your example that it's not, but it really doesn't hurt to double-check). You can do this withisinstance.if not isinstance(dictionary['dog'], list):