无法让 str 在 if-loop Python 3 中工作答案

【问题标题】：Cant get str to work in if-loop Python 3无法让 str 在 if-loop Python 3 中工作
【发布时间】：2015-03-02 18:43:41
【问题描述】：

我写了一个成绩计算器，你可以在其中放入一个浮点数，然后根据你的得分获得一个成绩。我的问题是我相信我需要一个 float(input... 但是如果你在框中写字母就会出错...

def scoreGrade():
"""
Determine the grade from a score
"""
gradeA = "A"
gradeB = "B"
gradeC = "C"
gradeD = "D"
gradeF = "F"

score = float(input("Please write the score you got on the test, 0-10: "))
if score >= 9:
    print("You did really good, your grade is:", gradeA, ". Congratulations")
elif score >= 7:
    print("Your results are good. They earn you a:", gradeB, ". Better luck next time")
elif score >= 5:
    print("Not too bad. You got a:", gradeC)
elif score >= 4:
    print("That was close...:", gradeD)
elif score < 4:
    print("You need to step up and take the test again:", gradeF)
else:
    print("Grow up and write your score between 0 and 10")

如果你写了分数从 0-10 的其他东西，有没有办法摆脱浮动并打印最后一条语句？

【问题讨论】：

这叫做“if 语句”，而不是“if-loop” :)
stackoverflow.com/questions/5424716/…
我删除了不必要的性别诽谤。这里不需要那种语言。
我是英国人。这个词仍然令人反感

标签： python string python-3.x

【解决方案1】：

类似这样的：

score = None
while score is None:
    try:
        score = float(input("Please write the score you got on the test, 0-10: "))
    except ValueError:
        continue

继续询问，直到 float 演员表起作用而不引发 ValueError 异常。

【讨论】：

【解决方案2】：

你可以这样做

try:
    score = float(input("Please write the score you got on the test, 0-10: "))
except ValueError:
    print("Grow up and write your score between 0 and 10")
    scoreGrade()

【讨论】：

【解决方案3】：

我建议使用EAFP 方法并分开处理好输入和坏输入。

score_as_string = input("Please write the score you got on the test, 0-10: ")
try:
    score_as_number = float(score_as_string)
except ValueError:
    # handle error
else:
    print_grade(score_as_number)

def print_grade(score):
"""
Determine the grade from a score
"""
gradeA = "A"
gradeB = "B"
gradeC = "C"
gradeD = "D"
gradeF = "F"

if score >= 9:
    print("You did really good, your grade is:", gradeA, ". Congratulations")
elif score >= 7:
    print("Your results are good. They earn you a:", gradeB, ". Better luck next time")
elif score >= 5:
    print("Not too bad. You got a:", gradeC)
elif score >= 4:
    print("That was close...:", gradeD)
elif score < 4:
    print("You need to step up and take the test again:", gradeF)
else:
    print("Grow up and write your score between 0 and 10")

请注意，通常您希望从函数返回，而不是在其中打印。使用函数输出作为 print 语句的一部分是细节，函数不必知道这一点。

【讨论】：