Using 'Not' to create a list inside a dictionary from a main list - Python

Question

I am trying to create a dictionary for Gray using the all_Artists list. His list need to include everything that is not in Isaac's list.

Isaac = {'fav_Artists': ['Little River Band', 'Juice Wrld', 'HP Boyz', 'Ne-Yo']}
Grays = {'fav_Artists': []}
all_Artists = ['Weird Al', 'Bruno Mars', 'Juice Wrld', 'Ricky Martin', 'HP Boyz', 'James Blunt', 'Ne-Yo', 'Paul McCartney', 'Little River Band']

for i in all_Artists:
  if not i in Isaac['fav_Artists']:
    Grays['fav_Artists'] = [i]

print(Isaac)
print(Grays)

The current output is:

{'fav_Artists': ['Little River Band', 'Juice Wrld', 'HP Boyz', 'Ne-Yo']}
{'fav_Artists': ['Paul McCartney']}

Can anyone tell me why I am only getting Paul and not the others?

Answer 1

You are setting Grays['fav_Artists'] to the new value each time. Basically, you are overwriting previous values with a new value, which is not what you want. Instead, use the append function:

Isaac = {'fav_Artists': ['Little River Band', 'Juice Wrld', 'HP Boyz', 'Ne-Yo']}
Grays = {'fav_Artists': []}
all_Artists = ['Weird Al', 'Bruno Mars', 'Juice Wrld', 'Ricky Martin', 'HP Boyz', 'James Blunt', 'Ne-Yo', 'Paul McCartney', 'Little River Band']

for i in all_Artists:
  if not i in Isaac['fav_Artists']:
    Grays['fav_Artists'].append(i)

print(Isaac)
print(Grays)

Answer 2

Give this a try.

Isaac = {'fav_Artists': ['Little River Band', 'Juice Wrld', 'HP Boyz', 'Ne-Yo']}
Grays = {'fav_Artists': []}
all_Artists = ['Weird Al', 'Bruno Mars', 'Juice Wrld', 'Ricky Martin', 'HP Boyz', 'James Blunt', 'Ne-Yo', 'Paul McCartney', 'Little River Band']
for artists in all_Artists:
    if artists not in Isaac['fav_Artists']:
        Grays['fav_Artists'].append(artists)