Dict already exists, and when I have a key, check whether dict[key] is None or not, and
I thought it would work like the code below, but it didn't work, so I'm asking you a question.
if (my_dict[key] != None):
KeyError: 3
my_dict = {}
if (my_dict[key] != None):
my_dict[key] = 1
else:
my_dict[key] += 1
If my_dict[key] finds a key that does not exist in dict (my_dict[key]), None is not returned, but KeyError.
So the code is
if key in my_dict:
my_dict[key] += 1
else:
my_dict[key] = 1
If you change it like this, it will work as you want.
However, we recommend that you write collections.defaultdict because this is already a Python standard function.
from collections import defaultdict
my_dict = defaultdict(int)
my_dict[key] += 1
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