dict value, how to change type from int to list?

[swissjoker]

I have a dictionary, and one of the keys currently has 1 as value, so the value side is an int. I'm trying to make the value side a list so it can have [1, 2].

I currently have: {'key1': 1}
I'm trying to get: {'key1': [1, 2]}

test = dict()
test['key1'] = 1

# i tried without success:
# this will do an addition
test['key1'] += 2
# this will replace the current value
test.update({'key1': 2})

thank you!