Python成绩计算器代码求助：百分比无法保留两位小数

我在Replit学习Python几周，现在写了一个成绩计算器程序，要求输入考试名称、满分和个人得分，输出保留两位小数的百分比成绩和对应等级。代码能运行，但百分比无法正确保留两位小数。以下是我的代码：

#intro
print("\033[31m" + "-----------------------" + "\033[0m")
print("Exam Grade Calculator📑")
print("\033[31m" + "-----------------------" + "\033[0m")
print()

#main
name_of_exam = input("What is the name of your exam?: ")
max_score = int(input("What was the maximum score?: "))
score = int(input("What was your score?: "))
print()

result = score / max_score
percent = round(result * 100, 2)

if percent >= 90:
  grade = "A+"
  print("You got", percent, "which is a", grade)

elif percent >= 80 and percent < 90:
  grade = "A-"
  print("You got", percent, "which is a", grade)

elif percent >= 70 and percent < 80:
  grade = "B"
  print("You got", percent, "which is a", grade)

elif percent >= 60 and percent < 70:
  grade = "C"
  print("You got", percent, "which is a", grade)

elif percent >= 50 and percent < 60:
  grade = "D"
  print("You got", percent, "which is a", grade)

else:
  grade = "F"
  print("You got", percent, "which is a", grade)

#outro
print()
print("\033[31m" + "-----------------------" + "\033[0m"

我尝试过修改百分比计算部分：

result = score / max_score
percent = result * 100
round(percent, 2)

也调换过计算和round的顺序，但问题依旧。

问题分析与修正方案 #

1. round函数未赋值的错误
   你第二次尝试的代码中，round(percent, 2)仅计算了结果，但没有将其赋值回percent变量，所以原变量数值未发生改变。正确写法应为percent = round(result * 100, 2)，但这只能解决四舍五入问题，无法强制显示两位小数（例如80.0会被打印为80.0而非80.00）。

2. 核心问题：输出未格式化
   Python打印float类型时会自动省略末尾的零，要强制保留两位小数，需使用字符串格式化，而非仅依赖round函数。

修正后的完整代码 #

#intro
print("\033[31m" + "-----------------------" + "\033[0m")
print("Exam Grade Calculator📑")
print("\033[31m" + "-----------------------" + "\033[0m")
print()

#main
name_of_exam = input("What is the name of your exam?: ")
max_score = int(input("What was the maximum score?: "))
score = int(input("What was your score?: "))
print()

result = score / max_score
percent = result * 100

# 简化条件判断逻辑
if percent >= 90:
    grade = "A+"
elif percent >= 80:
    grade = "A-"
elif percent >= 70:
    grade = "B"
elif percent >= 60:
    grade = "C"
elif percent >= 50:
    grade = "D"
else:
    grade = "F"

# 使用f-string格式化输出，强制保留两位小数
print(f"You got {percent:.2f}%, which is a {grade}")

#outro
print()
print("\033[31m" + "-----------------------" + "\033[0m")

关键修改说明 #

• 用{percent:.2f}在格式化字符串中完成四舍五入并强制显示两位小数，确保所有结果都以两位小数形式输出（如80变为80.00，85.5变为85.50）。
• 简化了条件判断，去掉了冗余的and percent < X，因为前面的条件已排除更高区间的情况。
• 修复了原代码末尾print语句缺少闭合括号的语法错误。

内容的提问来源于stack exchange，提问作者George