如何按条件控制输入提示显示 解决Python计算器第三个数输入提前弹出问题

• 第三个数的输入语句写在了条件判断外部，程序顺序执行时无论用户输入Y/N都会触发该提示
• 原有代码存在两处错误：N分支的求和逻辑错误包含了未使用的num3，且语句末尾缺失右括号

num1 = float(input("Enter a number: "))
num2 = float(input("Enter a second number: "))
question = input("Would you like to add another number? Y/N ")

if question == "Y":
    # 仅当用户选择Y时才触发第三个数的输入请求
    num3 = float(input("Enter a third number: "))
    print(num1 + num2 + num3)
elif question == "N": 
    print(num1 + num2)

可以对用户输入做兼容处理，支持大小写、多余空格的输入场景：

num1 = float(input("Enter a number: "))
num2 = float(input("Enter a second number: "))
# 去除输入首尾空格后转大写，兼容y/n、带空格的输入
question = input("Would you like to add another number? Y/N ").strip().upper()

if question == "Y":
    num3 = float(input("Enter a third number: "))
    print(num1 + num2 + num3)
elif question == "N": 
    print(num1 + num2)
else:
    print("输入无效，请输入Y或N")

内容的提问来源于stack exchange，提问作者Caio