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Python

Posted by newpal
newpal
1,717 Points

What is wrong with my code please?

Let's use str to turn Python code into Morse code! OK, not really, but we can turn class instances into a representation of their Morse code counterparts.

I want you to add a str method to the Letter class that loops through the pattern attribute of an instance and returns "dot" for every "." (period) and "dash" for every "_" (underscore). Join them with a hyphen.

I've included an S class as an example (I'll generate the others when I test your code) and it's str output should be "dot-dot-dot".

morse.py 
class Letter:
    outcome1 = ""
    outcome2 = ""
    def __init__(self, pattern=None):
        self.pattern = pattern

    def __str__(self):
        for attribute in self.pattern:
            if attribute == '.':
                outcome1 += "dot-"
            elif attribute == '_':
                outcome2 += "dash-"
        return outcome1 + outcome2

class S(Letter):
    def __init__(self):
        pattern = ['.', '.', '.']
        super().__init__(pattern)
newpal
newpal
1,717 Points

Thanks Steven! What about this code:

class Letter:
    outcome = ""
    def __init__(self, pattern=None):
        self.pattern = pattern

    def __str__(self):
        for attribute in self.pattern:
            if attribute == '.':
                outcome += "dot-"
            elif attribute == '_':
                outcome += "dash-"
        outcome_list = list(outcome)
        outcome_list.pop()
        outcome = str(outcome_list)
        return outcome

class S(Letter):
    def __init__(self):
        pattern = ['.', '.', '.']
        super().__init__(pattern)

1 Answer

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

It looks like this code will put all the dots together and all the dashes together, and then combine them so the dots come first. But for correct Morse, the order must be the same as the symbols in the pattern. For example, ".." should come out as "dash-dot-dot-dash", instead of "dot-dot-dash-dash-".

And it looks like you'll end up with a trailing hyphen after the last word, I'd expect the challenge to also consider that an error.

newpal
newpal
1,717 Points

Thank you Steven for your explanation. I tried to solve the issues you pointed out. However, the code is till not passing. class Letter: outcome = "" def init(self, pattern=None): self.pattern = pattern def str(self): for attribute in self.pattern: if attribute == '.': outcome += "dot" if attribute != self.pattern[-1]: outcome += "-" elif attribute == '_': outcome += "dash" if attribute != self.pattern[-1]: outcome += "-" return outcome

class S(Letter): def init(self): pattern = ['.', '.', '.'] super().init(pattern)

newpal
newpal
1,717 Points 
class Letter:
    outcome = ""
    def __init__(self, pattern=None):
        self.pattern = pattern
    def __str__(self, pattern):
        for attribute in self.pattern:
            if attribute == '.':
                outcome += "dot"
                if attribute != self.pattern[-1]:
                    outcome += "-"
            elif attribute == '_':
                outcome += "dash"
                if attribute != self.pattern[-1]:
                    outcome += "-"
        return outcome

class S(Letter):
    def __init__(self):
        pattern = ['.', '.', '.']
        super().__init__(pattern)
Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

This time, it looks like a hyphen will only be added it the current item is different from the last one. But that would mean a pattern like "S" would come out as "dotdotdot". The original idea of adding a hyphen every time wasn't bad, you'd just need to "slice" the last one off.

Also, the initialization of "outcome" seems to have gotten lost in the revision. And the function should not require an argument since the "pattern" is already in the instance.

newpal
newpal
1,717 Points

Thanks Steven! What about this code:

class Letter:
    outcome = ""
    def __init__(self, pattern=None):
        self.pattern = pattern

    def __str__(self):
        for attribute in self.pattern:
            if attribute == '.':
                outcome += "dot-"
            elif attribute == '_':
                outcome += "dash-"
        outcome_list = list(outcome)
        outcome_list.pop()
        outcome = str(outcome_list)
        return outcome

class S(Letter):
    def __init__(self):
        pattern = ['.', '.', '.']
        super().__init__(pattern)
Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

Converting a string into a list like that probably doesn't do what you're expecting. You might need to use "split" for that.

But you don't need to do all the conversion. That's why i was hinting that you might need to "slice" off the last character.

newpal
newpal
1,717 Points

How do you slice off the last character? I tried slicing off the last character in the code below:

class Letter:
    output = ""
    def __init__(self, pattern=None):
        self.pattern = pattern

    def __str__(self):
        for item in self.pattern:
            if item == '.':
                output += "dot-"
            elif item == '_':
                output += "dash-"
        output = output[:-1]
        return output

class S(Letter):
    def __init__(self):
        pattern = ['.', '.', '.']
        super().__init__(pattern)
newpal
newpal
1,717 Points

My code still throws an error!

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

The "slice" is exactly right. The only remaining issue is that the initialization of "output" needs to be moved into the function so it will start fresh each time the function is used.

Otherwise, I think you've got it! :+1:

newpal
newpal
1,717 Points

Thank you Steven for your comments. It took me a while to solve this challenge but my code solves the challenge now! Thank you for your help!