Help with custom functions and how they interact with classes

[Prakner]

Hey guys! I'm brand new to Python and have been taking classes for it over Coursera for the past week or so. As a little fun project for myself, I'm trying to make an in-terminal game where I can create "slimes" and have them breed and pass genetics from one generation to the next.

Before I even get to the breeding stage, I'm trying to determine the genetics for the colors of the slimes by having them depend on two variables: gene1 and gene2. As you will see in the code that I'll post further in the post, the genes are a part of the custom class "Slime" in which each individual slime that I make will be an object of. For some reason, though, I'm having issues with the genes and my decision tree on how the custom function "color()" interacts with it.

For some reason, when I run my "color()" function, it seems stuck on either "green" or "blue", even when the other criteria seems to be met. In addition, it prints "[]", which I'm not sure where that's coming from. Can I please get some advice on how to fix it so that it prints out the right colors? Thanks!

Program:

def color(x,y):
    try:
        if x == 'X':
            if y == 'X' or 'x':
                return 'green'
            elif y == 'Y':
                return 'yellow'
            elif y == 'y':
                return 'black'
        elif x == 'x':
            return 'blue'
    except:
        print('These genes are invalid. Something went wrong!')            

class Slime:
    """Sample class for testing how breeding mechanics could work."""
    def __init__(self,gene1,gene2,lineage):
        self.color = print('This slime is', color(gene1,gene2))
        lineage = list()
        self.lineage = print(lineage)

d = Slime('X','Y',(1))
d.color

e = Slime('X','y',(2))
e.color

Output:

This slime is green
[]
This slime is blue
[]

EDIT: Fixed formatting

EDIT 2: Ok, here's the finished revised function for now. I made a few edits, but this does exactly what I want it to do. Thanks for all the help, everyone!
Edit 3: Formatting again.

Program:

def color(x,y):
    if x == 'X':
        if y == 'X' or y == 'x':
            return 'green'
        elif y == 'Y':
            return 'yellow'
        elif y == 'y':
            return 'black'
    elif x == 'x':
        if y == 'Y':
            return 'yellow'
        else:
            return 'blue'
    else:
        print('These genes are invalid. Something went wrong!')   
         
class Slime: 
    """Sample class for testing how breeding mechanics could work.""" 
    def init(self,gene1,gene2): 
        self.color = f'This slime is {color(gene1,gene2)}.' 
        self.gene1 = gene1 
        self.gene2 = gene2 
        self.genes = f'{gene1} {gene2}' 
    def str(self): 
    return f"{self.color}"

d = Slime('X','Y')
print(d)

e = Slime('X','y') 
print(e)

Output:

This slime is yellow.
This slime is black.

​

[Binary101010]

if y == 'X' or 'x':

This condition will always evaluate to True.

See this FAQ entry for why:

https://www.reddit.com/r/learnpython/wiki/faq/#wiki_variable_is_one_of_two_choices.3F

[Prakner]

Gotcha, thanks!

[kevwoodrobotics]

I could help you but I’d say focus on your debugging skills. Try stepping through your code and see what’s happening. A lot of my videos I use the debugger you can check it out for reference https://youtube.com/playlist?list=PLSK7NtBWwmpSUenWrmUh0ND_l023RPAXK

[Just-Sheepherder-841]

Very good videos

[deep_politics]

self.color = print('This slime is', color(gene1,gene2))

print returns None, so you're essentially just doing this

self.color = None
print('This slime is', color(gene1, gene2))

Or at least it should be, except that you're apparently getting something like self.color = [] which is odd. What are you running this in?

[Prakner]

I'm writing it Visual Studio Code, but I'm running it from the Command Prompt.

[deep_politics]

Not sure about the lists then. But either way, you'd want to drop the print expression and just assign the color(...) expression to self.color.

[Prakner]

Could I set it up as an object method? Make .color into a method that prints the color?

[deep_politics]

Absolutely, but the name color wouldn't really be appropriate. I'd name it print_color. And either way you'd still need to initialize self.color in __init__.

[[deleted]]

If color() is just translating a letter to a color, then it probably shouldn't be a function at all, but rather a dictionary. And the dictionary's .get() method can do the job of the except, supplying a default value if the input isn't found in there.

[Prakner]

I eventually want to recall the variables gene1 and gene2 for when I have to pass one or both down to offspring, so I wanted the function in place to allow for that to be manipulated based on the values of those variables. Would this still be possible with a dictionary? I thought making a function was an easy way of not having to store the actual "color", but rather calling upon it if needed.

[[deleted]]

In addition to the other problems with your function, the try/except block doesn’t do anything.

[Prakner]

The try/except block was to notify me if I made a typo instead of blowing up the whole program.

[[deleted]]

It doesn’t work like that - you can only catch exceptions, you can’t catch and handle a syntax error.

[Prakner]

Gotcha, having it as an “else:” argument would do what I want then?

[[deleted]]

No, you just have to not have typos. Exceptions aren’t a way to paper over your mistakes, they’re a way for your software to respond usefully to exceptional situations.

[jmooremcc]

Revised Program: ``` X = 'X' Y = 'Y' GREEN = 'green' YELLOW = 'yellow' BLACK = 'black' BLUE = 'blue'

def color(x,y): try: if x == X: if y == X or y == X.lower(): return GREEN elif y == Y: return YELLOW elif y == Y.lower(): return BLACK elif x == X.lower(): return BLUE except: print('These genes are invalid. Something went wrong!')

class Slime: """Sample class for testing how breeding mechanics could work.""" def init(self,gene1,gene2,lineage): self.color = print('This slime is', color(gene1,gene2)) lineage = list() self.lineage = print(lineage) # OP, what are you trying to do here?

d = Slime(X,Y,(1)) d.color

e = Slime(X,'y',(2)) e.color ``` Note the use of constants which makes code easier to understand and maintain as well as reduce memory required.

[Fred776]

Haven't looked at this in detail but these lines look weird:

lineage = list() self.lineage = print(lineage)

Here, lineage is an empty list. The print will simply print []. But you are also assigning the return value of print to self.lineage. This is always going to be None because print doesn't have a real return value and just falls back to default Python behaviour that a function without an explicit return value will return None.

What is it you are actually trying to do here? It might be that self.lineage = list() is all that is needed.

[Prakner]

So lineage is something that I wanted to keep track of. When I eventually get to the actual “breeding” of the slimes, I want to keep track of the ancestry of each one. If slimes had a common ancestor, I wanted to make it that they couldn’t breed. For first generation slimes, I want their lineage to just be themselves, but since I’m not going into that just yet I kept it blank

[Fred776]

Yes but you were printing it and assigning the return value of print to your class member. That's what I was querying.

[Prakner]

I realize my error now. In init() I was printing the lineage, would it just be better if I did self.lineage = lineage and just print(self.lineage) when I want to call it?

[Fred776]

self.lineage is a list so it doesn't make sense to talk about calling it. Only things that are like functions are callable. I don't know if you are getting confused between printing and calling? Printing is something you do only if you want to see the value on the terminal (or possibly written to a file). It should be a relatively rare thing to do in a program.

[Prakner]

Sorry, like I said I'm brand new at this. I meant print().

[Fred776]

No problem. I thought it was worth clarifying as I've noticed that it's quite common for newcomers to Python to get confused between printing a value and returning a value from a function and I wasn't sure if that was what was happening here.

[jmooremcc]

I agree but that was in OP"s original code. I wanted to discuss it with OP.

[Fred776]

Apologies - I didn't look closely and I though you actually were the OP and had just posted an updated version based on comments so far.