Python 3-为什么我在这个作业问题中的 try 和 except 函数没有编译？ [关闭]

Question

我的循环作业需要帮助！

我是 Python 3.7 的新手，遇到一个作业问题，需要我使用多个语句来查找用户输入的最小值和最大值。我知道我必须创建一个循环语句。但是，我卡在提示的第二部分。

我还必须创建一个 try + except 函数，这样当用户输入字符串时，就没有回溯了。

当我尝试编译时，我收到：

SyntaxError: 第 16 行的“返回”外部函数

能否有更高级的 Python 人士，看看我的语法 + 语句，让我知道其中一个地方是否有错误 + 下次要注意什么？

以下是显示原始硬件提示和我尝试解决它的两个屏幕截图。

 
largest = None
smallest = None
fval = float(val)

while True:
    val = input("Enter a number: ")
    fval = float(val)
    if val == "done":
        break
    print(fval)

    if smallest is None:
        smallest = fval
    elif fval > smallest :
        fval = smallest
    return fval

    if largest is None:
        largest = fval
    elif fval > largest :
        largest = fval
    return fval

try :
    int(astr)

except :
    print("invalid output")

print("Minimum", smallest)
print("Maximum", largest)

非常感谢！

Original Homework Prompt

My Code Written Out

Answer 1

这是简单的答案。它需要在一个函数中。创建一个函数，然后将 while 循环放入其中。

Answer 2

首先让我们注释我在您的原始代码中看到的一些机会：

largest = None
smallest = None
fval = float(val)    ## "val" here has no definition and is a problem

while True:
    val = input("Enter a number: ")
    fval = float(val)    ## if the user entered "done" this will be a problem here
    if val == "done":
        break
    print(fval)

    if smallest is None:
        smallest = fval
    elif fval > smallest :  ## you want to test if our new value is less than the current smallest one not greater than it
        fval = smallest
        return fval     ## "return" is only valid in the context of a method/function

    if largest is None:
        largest = fval
    elif fval > largest :
        largest = fval
        return fval     ## "return" is only valid in the context of a method/function

try :
    int(astr)    ## "astr" here has no definition and is a problem

except :
    print("invalid output")

print("Minimum", smallest)
print("Maximum", largest)

那么，我们该如何清理一下...

largest = None
smallest = None

while True:
    val = input("Enter a number: ")

    ##---------------------------
    ## Ask for numbers until the user gives us the string "done"
    ## If they do, we "break" out of this while loop
    ##---------------------------
    if val == "done":
        break
    ##---------------------------

    ##---------------------------
    ## try to get the input as an integer and if not an integer ignore it
    ## per our instructions by "continuing" to the next iteration of our while loop
    ##---------------------------
    try:
        fval = int(val)
    except ValueError as e:
        print(f"\"{val}\" is not a valid integer or the command \"done\"")
        continue
    ##---------------------------

    ##---------------------------
    ## update our tracking of smallest if appropriate
    ##---------------------------
    if smallest is None or fval < smallest:
        smallest = fval
    ##---------------------------

    ##---------------------------
    ## update our tracking of largest if appropriate
    ##---------------------------
    if largest is None or fval > largest:
        largest = fval
    ##---------------------------

print(f"Minimum: {smallest}")
print(f"Maximum: {largest}")