python - 如何在 Python 中更新字典中键的值？

Question

我有一本代表书店的字典。键代表书名，值代表该书的份数。当书籍从商店出售时，书籍的份数必须减少。

我已经编写了一个代码来减少已售图书的份数，但是在更新后打印字典时，我得到的是初始字典而不是更新后的字典。

 n = input("Enter number of books in shop: ")

 book_shop = {} # Creating a dictionary book_shop

 # Entering elements into the dictionary
 for i in range(n):
     book_title = raw_input("Enter book title: ")
     book_no = input("Enter no of copies: ")
     book_shop[book_title] = book_no

 choice = raw_input("Do you want to sell?")
 if (choice in 'yesYES'):
        for i in range(n):
             print("Which book do you want to sell: ", book_shop)
             ch1 = raw_input("Enter your choice: ")
             if(book_shop.keys()[i] == ch1):
                    book_shop.keys()[i] = (book_shop.values()[i]-1)
                    break
        
 print(book_shop)

我想以最简单的方式解决问题。我是否遗漏了代码中的任何逻辑或任何行？

Answer 1

好吧，您可以通过引用键直接从值中减去。我认为哪个更简单。

>>> books = {}
>>> books['book'] = 3       
>>> books['book'] -= 1   
>>> books   
{'book': 2}   

在你的情况下:

book_shop[ch1] -= 1