Python3简易书店程序报错求助：NameError变量未定义问题排查

Hey there! Let's fix that frustrating NameError you're seeing in your bookstore program.

错误原因分析 #

The NameError: name 'book_choice' is not defined error means exactly what it says: you tried to use the variable book_choice (and probably book_price too) when calling your book_store function, but you never created or assigned a value to those variables first. Python has no idea what book_choice refers to because you didn't tell it!

修复后的完整代码 #

Here's a working version of your program that includes user input and fixes the variable definition issue:

# 定义处理订单的函数
def book_store(book, price):
    # 返回格式化后的订单信息
    return f"order: '{book}' costs '{price} dollar'"

# 从用户输入获取书籍名称和价格，定义所需变量
book_choice = input("Enter the name of the book you want: ")
book_price = input("Enter the price of the book: ")

# 调用函数并打印结果
print(book_store(book_choice, book_price))

关键修复点 #

• We added input() calls to collect user input and assign those values to book_choice and book_price. Now Python recognizes these variables when we pass them to the book_store function.
• The function itself uses an f-string to format the output exactly as you wanted—clean and readable.

额外优化建议 #

If you want to make the price display more polished (like handling numbers properly instead of strings), you can convert the price input to a float:

book_price = float(input("Enter the price of the book: "))
# 调整函数里的字符串格式，让价格显示更自然
def book_store(book, price):
    return f"order: '{book}' costs ${price:.2f}"

This will show the price as a currency value (e.g., $19.99 instead of '19.99 dollar').

内容的提问来源于stack exchange，提问作者user9126689