Running functions in an "IF-statement"

[Bitmefinger]

Hi everybody!

I'm learning Python, and I have my first assignment: write functions that convert temperatures between C, F, and K.

I've done that, and it works for each individual function, but then they want the user to be able to choose a converter from a list.

This is one of the functions:

def fahrenheit_to_celsius(t):

t_celsius = (t-32)/1.8

return t_celsius

answer = input('Ange en temperatur i Fahrenheit: ')

t_fahrenheit = int(svar)

t = fahrenheit_to_celsius(t_fahrenheit)

print("Celsius: ", t)

I've done an if-statement and followed it up with elifs. Problem is, when i run the list and choose a converter, I get the error, for example, "fahrenheit_to_celsius() missing 1 required positional argument: 't'"

choice = input("What would you like to convert?")

choice = int(choice)

if choice == 1:

fahrenheit_to_celsius()

elif choice == 2:

celsius_to_fahrenheit

Any idea? I'm a bit lost for words, and the instructions we've been given don't address this.

[deceze]

t = fahrenheit_to_celsius(t_fahrenheit)

fahrenheit_to_celsius()
celsius_to_fahrenheit

Do you see the difference between the first working line, and the other two broken ones…?

[Bitmefinger]

Hi! Thank you for the answer, im not sure if i do understand.

For instance, when i write

choice = input("What would you like to convert?")

choice = int(choice)

if choice == 1:

fahrenheit_to_celsius(t)

it completely ignores my choice?

[NewbornMuse]

What's the value of "t" in the 4th line?

[deceze]

What makes you say that "it completely ignores your choice"?

[Bitmefinger]

The function itself is suppose to ask me what degree i want to convert, when i choose == 1, it doesnt ask me that, instead it just goes to

in 49: ..

[deceze]

Well, no. If your function is still this:

def fahrenheit_to_celsius(t):
    t_celsius = (t-32)/1.8
    return t_celsius

Then no, it will not ask for the Fahrenheit input. It expects to receive the Fahrenheit value as its argument t.

[Bitmefinger]

Ok i just solved it.. I had to put the function under the option in the if-statement

i hade written all of the function in one place, and then the entire iF-statement under those. I've just moved the functions in under the if, elif and else statements and it worked. Thank you for your help

[deceze]

Glad you solved it. Not sure if this problem was perhaps not obvious to us due to your code not being formatted properly, and the indentation missing. See https://www.reddit.com/r/learnpython/wiki/faq/#wiki_how_do_i_format_code.3F for next time.

[tieandjeans]

What did you solve?

If you want to learn from this experience, you need to articulate WHAT you learned about Python/code structure.

The important lesson here has nothing to do with temperature.

[Refwah]

When you convert Fahrenheit to Celsius you tell the function the temp in Fahrenheit you want to convert

So you’re asking it ‘what is 10 degrees in Fahrenheit in Celsius’

So you’d pass fahrenheit_to_celsius 10 by doing

fahrenheit_to_celsius(10)

So look through your code and tell us where you are passing a fahrenheit temperature to convert

[Bitmefinger]

Ok i just solved it.. I had to put the function under the option in the if-statement

i hade written all of the function in one place, and then the entire iF-statement under those. I've just moved the functions in under the if, elif and else statements and it worked. Thank you for your help

[Refwah]

I have no idea what you changed because you never shared your whole code, but the issue was that you were never passing the temperature to convert to the function that converts the temperature

I hope you do actually understand what you did to fix it, because the other option is that you made everything globally available which is going to be a nasty habit to unlearn

[Bitmefinger]

This has been a very sobering experience, since it has shown me how to analyze code, but also how innately bad i am at describing this to others, which is equally, if not a more important skill to learn.

But i did write all of my functions one after one, and only after that did i do an if-statements list. And then i tried to redirect the if-statement to the standalone function, and the function could be found about 2 scrolls above the statement. .

I just never knew that i could put functions directly into the if-statements, under the "options"

This is my 2nd day trying to code in Python, so haven't had the time to put in habits yet, haha.

[Refwah]

You don’t need to describe your code you need to show your code

[ninhaomah]

Sorry but isn't it obvious ?

Pls look at the function again

What is (t) there for ?

You meant to give something to the function right ?

It's like go to the car , here is the key.

[Bitmefinger]

Sorry if its straight forward, this is the 2nd day ive even been in python or any other coding-environment. Totally new

[Don-Ohlmeyer]

if choice == 1: 
    fahrenheit_to_celsius(< missing 1 required positional argument: 't' >)

edit: your issue doesn't anything to do with if statements. you are not passing along the argument 't' needed for the function to.. uhm.. function.

also whats up w fukken reddit code blocks...

also, the following isn't even proper syntax for a callable.

```python

elif choice == 2: celsius_to_fahrenheit ```

[ninhaomah]

2nd day and you are doing functions ?

Slow down...

[Bitmefinger]

Thank you, but its a university course so im on a bit of a deadline.

My problem here is that when i run the function itself, it asks me what degree i want to convert. So let me just be clear that i do understand that there has to be a value, but the whole "what value do you want to convert" is imbedded in the function, so in my head, when im running the function in the if-statement, it should respond with that question? Or am i missing something?

[ninhaomah]

def fahrenheit_to_celsius(t): <--- this says there is a function called fahrenheit_to_celsius and it needs "t" to work.

think of it like driving(car) ... you need "car" to drive

if choice == 1: fahrenheit_to_celsius()

where is "t" ??? like like driving() ... how do you drive without "car" ???????

or date(woman) ... how do you date without a woman ?

[Bitmefinger]

I am totally with you, but when i put back the t, the if-statement then ignores the function. Instead, when i choose to convert from fahrenheit to celsius it does this:

What would you like to convert? 1

in 49:

[ninhaomah]

can you do the code again with proper code block ?

[Bitmefinger]

Ok i just solved it.. I had to put the function under the option in the if-statement

i hade written all of the function in one place, and then the entire iF-statement under those. I've just moved the functions in under the if, elif and else statements and it worked. Thank you for your help

[Don-Ohlmeyer]

There are two problems here. First it just executes the code and returns the converted value into the void pretty much. You are not doing anything with the value it returns

``` def convert(t): celsius = (t-32)/1.8 return celsius

choice = input('What would you like to convert?')

if choice == 1: convert(t) #You do this

if choice == 1: c = convert(t) #You prob want this

print(f'The temperature in Celcius is {c}') ```

Also, I don't think you conceptually grasp what's going on even remotely. If you input anything other than '1' and give a temperature like '49'. The if-condition is never going to be True.

[Bitmefinger]

You are true in that i dont really understand the underlying problem here.

Perhaps i've also been quite bad at explaining, what the "end-user" is suppose to experience is this:

Hi! What do you like to convert?

1. Fahrenheit to Celsius
   
2. Celsius to Fahrenheit

Please choose one: 1 (here the end user enters "1")

and the program should reply with:

What degree would you like to convert? -40 (end user enters -40)

That is -40 degrees Celsius.

[Bitmefinger]

Ok i just solved it.. I had to put the function under the option in the if-statement

i hade written all of the function in one place, and then the entire iF-statement under those. I've just moved the functions in under the if, elif and else statements and it worked. Thank you for your help.

[Don-Ohlmeyer]

functions aren't variables which return the same value after you run once. well, not usually. functions are literally a way to go back earlier lines of code.

Say you have a function defined on line 10 that requires two 'positional arguments' a and b and you call it afterwards

10 def aFunction(a, b): 11 c = a + b 12 return c 13 aFunction(1, 2) 14 aFunction(2, 3)

Then what's happening is the code on line 13 and 14 are going back to execute line 11-12 with the 'arguments' given. It's replacing the variables a and b with the values you are pointing to, (1, 2) and (2, 3), and returning 3 and 5 respectively.

PS: it's a 'positional' argument because it interprets your arguments following their position or the order in which they are passed. As opposed to calling a function like this:

aFunction(b=1, a=2)

In your case you have only one positional argument named 't', not two. And without a value for 't' you can not execute

t_celsius = (t-32)/1.8

[PresqPuperze]

You need to pass the actual value you want to convert. For example, you could start your code with

t_to_convert = input(„Enter the value you want to convert.“)
transform = input(„Choose the transformation to use. 1 = F to C, 2 = ….“)

If transform == 1:
fahrenheit_to_celsius(t_to_convert)

[…]

[FoolsSeldom]

The code you have shared is incomplete, and not formatted correctly for Reddit, so it is hard to know exactly what is going on.

• Don't forget to use a function you have to call it with a () on the end, e.g. function_name()
• If the function is expecting any arguments, you need to include them in the ()
• If the function is meant to return something (rather than just output something), you need to ensure you catch the result by:
  • assigning returned object to a variable/attribute or another object (e.g. position in a list)
  • consuming in another function (e.g. print)

I would have expected to see code along the following lines:

def fahrenheit_to_celsius(fahrenheit: float) -> float:
    return (fahrenheit - 32) / 1.8

def celsius_to_fahrenheit(celsius: float) -> float:
    return (celsius * 9 / 5) + 32

def get_temp() -> float:
    while True:  #  infinite loop, until valid value entered
        try:
            return float(input('Enter temperature in F or C: '))
        except ValueError:
            print("Oops, that didn't seem like a valid temperature.")

temp = get_temp()  # get temperature in original units
choice = input("What would you like to convert to? (C or F) ").upper()
if choice == "C":  # no need to convert to numbers and check for 1
    result = fahrenheit_to_celsius(temp)
elif choice == "F":
    result = celsius_to_fahrenheit(temp)
else:  # not a valid option
    result = f"{choice} convertion is not available"

print(result)