有人能告诉我我的代码有什么问题吗

Question

I am a beginner coder and would just like to say thanks for the help. I probably made some rookie mistakes but that's why I'm here to learn. I cant figure out what's wrong but lets say I plug in a string (50,K,C) it should convert 50 Kelvin to Celsius but my code does nothing

def temperature_converter(value, scale_from, scale_to):

    if scale_from == "F" and scale_to == "C":
        (value -32)* 5 / 9 for F to C
        return
    elif scale_from == "F" and scale_to == "K":
        (value * 5 / 9) + 273 for F to K
        return
    elif scale_from == "C" and scale_to == "F":
        value * (9 / 5) + 32  for C to F
        return
    elif scale_from == "C" and scale_to == "K":
        (value + 273) for C to K
        return
    elif scale_from == "K" and scale_to == "F":
        9/5 * (value - 273) + 32 for K to F
        return
    elif scale_from == "K" and scale_to == "C":
        value - 273 for  K to F
        return

Answer 1

Okay, lets take it bit by bit:

1. for F to C and other similar "statements" you have in your code are not valid python. Plus, they seem to serve no purpose, so I have removed them below.
2. Operations performed on variables are not done in-place. When you do (value -32)* 5 / 9 , you must store that result somewhere. value will remain the same throughout, unless you assign a value to it.
3. When you return , you have to return something . Just having the return keyword there doesn't do anything.

Here is a revised version of your code. I have deliberately made the first and second case (F to C, F to K) more verbose to illustrate point 2:

def temperature_converter(value, scale_from, scale_to):
    if scale_from == "F" and scale_to == "C":
        a = (value -32)* 5 / 9 #Assign the modified value to a variable
        return a
    elif scale_from == "F" and scale_to == "K":
        value = (value * 5 / 9) + 273 #The value variable can be reused
        return value
    elif scale_from == "C" and scale_to == "F":
        return value * (9 / 5) + 32 #Always return something. Don't have just the keyword
    elif scale_from == "C" and scale_to == "K":
        return value + 273
    elif scale_from == "K" and scale_to == "F":
        return 9/5 * (value - 273) + 32 
    elif scale_from == "K" and scale_to == "C":
        return value - 273

A couple of extra points:

• It is advisable to bunch up your cases, as I will demonstrate below. IMO it makes for more readable code.
• You should always standardize your input. Take the possibility of the user entering "f" in lowercase into account in this case.
• Account for being given bogus arguments.

Final code would be:

def temperature_converter(value, scale_from, scale_to):
    scale_from = scale_from.upper() #Make all arguments upper case
    scale_to = scale_to.upper() 

    if scale_from == "F": #Group cases together
        if scale_to == "C":
            return (value -32)* 5 / 9
        elif scale_to == "K":
            return (value * 5 / 9) + 273
    elif scale_from == "C":
        if scale_to == "F":
            return value * (9 / 5) + 32
        elif scale_to == "K":
            return value + 273
    elif scale_from == "K":
        if scale_to == "F":
            return 9/5 * (value - 273) + 32
        elif scale_to == "K":
            return value - 273

    raise ValueError("Invalid argument") #Have predictable behavior if invalid input is given

Answer 2

We might as well give to the correct conversion formulas while you're here

def temperature_converter(value, scale_from, scale_to) :

    if scale_from == "F" and scale_to == "C" :
        return (value - 32.0) * 5 / 9 #for F to C
    elif scale_from == "F" and scale_to == "K":
        return (value + 459.67) * 5 / 9 #for F to K
    elif scale_from == "C" and scale_to == "F":
        return value * (9.0 / 5.0) + 32  #for C to F
    elif scale_from == "C" and scale_to == "K":
        return value + 273.15 #for C to K
    elif scale_from == "K" and scale_to == "F":
        return ((value - 273.15) * 1.8) + 32 #for K to F
    elif scale_from == "K" and scale_to == "C":
        return value - 273.15 #for  K to C

Then call it like this

result = temperature_converter(50, "F", "C")

or this

result = temperature_converter(50, 'F', 'C')

I think you might have been calling the function wrong, as well.

There is a very important thing that you might not know, and nobody here told you yet. It could potentially cause you major headaches trying figure out why you are getting the wrong values.

There are integers and floating point numbers (or floats ). To put it simply, integers are whole numbers, but floats can use decimals and fractional values.

If you use only integers it will round the values to a whole number. I noticed this in a big way with the Celsius to Fahrenheit conversion. When I used 9 / 5 instead of 9.0 / 5.0, it rounded the value a lot, and my answer was way off. This is because it was rounding 9 / 5 to a whole number, instead of 9 / 5 = 1.8.

So keep that in mind. Make sure your Python interpreter is using floats (decimal values) in the way you're expecting, and it's doing the math the way you want.

I included decimal points in all the formulas, so Python was using floats for the math. (At least my Python interpreter was.)

Also, double check the formulas.

Edit:

Don't forget to print your answer

print(result)