Well you could directly substract from the value by just referencing the key. Which in my opinion is simpler.
>>> books = {}
>>> books['book'] = 3
>>> books['book'] -= 1
>>> books
{'book': 2}
In your case:
book_shop[ch1] -= 1
Well you could directly substract from the value by just referencing the key. Which in my opinion is simpler.
>>> books = {}
>>> books['book'] = 3
>>> books['book'] -= 1
>>> books
{'book': 2}
In your case:
book_shop[ch1] -= 1