Python温度转换输入合法性校验的异常处理问题求助

Hey there! Let's break down what's going wrong with your code and fix it step by step—you're on the right track with try/except, just a few missteps in how you're validating inputs.

First, let's go over the key issues in your original code:

• Temperature conversion check: tempin == int(tempin) doesn't actually convert the input to an integer, nor will it trigger an error properly. If the input isn't a number, int(tempin) will throw a ValueError, but you're just doing a comparison here instead of attempting to assign the converted value.
• Scale validation logic: scalein == "C" or "F" or "K" is a common Python gotcha. This line doesn't check if scalein is one of those three letters—instead, it evaluates to (scalein == "C") or "F" or "K", and since non-empty strings are always True, this condition will never fail no matter what you input.
• Wrong exception type: You're catching NameError, but that's for when you reference a variable that doesn't exist. The error you'll get from invalid numeric input is ValueError. Also, invalid scale inputs aren't exceptions—they're just invalid values we need to check manually.

Here's a fixed version of your function that does proper input validation with try/except for the temperature and manual checks for the scales:

def gettemp():
    while True:
        # Validate temperature input (must be integer)
        try:
            tempin = int(input("Enter temperature value: "))
        except ValueError:
            print("Oops! That's not a valid integer. Please reenter.")
            continue
        
        # Validate input scale (handle case insensitivity and extra spaces)
        scalein = input("Enter temperature scale (C/F/K): ").strip().upper()
        if scalein not in ["C", "F", "K"]:
            print("Invalid input scale! Please use only C, F, or K.")
            continue
        
        # Validate output scale
        scaleout = input("Enter scale to convert to (C/F/K): ").strip().upper()
        if scaleout not in ["C", "F", "K"]:
            print("Invalid output scale! Please use only C, F, or K.")
            continue
        
        # All inputs are valid—return them
        return tempin, scalein, scaleout

# Test the function
print(gettemp())

Let me walk through what this does:

1. Temperature validation: We wrap int(input(...)) in a try block. If the user enters something that can't be converted to an integer (like a string or decimal), it triggers a ValueError, we print an error message, and the loop starts over.
2. Scale validation: We use .strip().upper() to handle accidental spaces and case insensitivity (so users can enter lowercase c/f/k too). Then we check if the input is in our allowed list—if not, we prompt again.
3. Loop until valid: The while True loop keeps running until all inputs pass validation, at which point we return the valid values.

This way, the function won't return anything until the user provides a valid integer temperature and valid scale letters.

备注：内容来源于stack exchange，提问作者Dr. H