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Python

Posted by ashleytan
ashleytan
6,131 Points

I'm not sure what I'm missing (TypeError: from_string() missing 1 required positional argument)

I'm not entirely clear on what I'm supposed to do and I'm not sure what the error means either - TypeError: from_string() missing 1 required positional argument

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

    def __iter__(self):
        yield from self.pattern

    def __str__(self):
        output = []
        for blip in self:
            if blip == '.':
                output.append('dot')
            else:
                output.append('dash')
        return '-'.join(output)

    def from_string(self, spoken_morse):
        spoken_morse = spoken_morse.split["-"]
        written_morse = []

        for blip in spoken_morse:
            if blip == "dash":
                written_morse.append("_")
            elif blip == "dot":
                written_morse.append(".")
        self.pattern =  written_morse

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

2 Answers

Kip Yin
Kip Yin
4,847 Points

So here you need to define a classmethod called from_string, which returns an instance of the class Letter.

Firstly, your from_string() is not a classmethod. Simply wrap the function with@classmethod and change self to cls:

@classmethod
def from_string(cls, spoken_morse):
    # the rest of the code

Secondly, this class method needs to return an instance of Letter with written_morse as its argument:

@classmethod
def from_string(cls, spoken_morse):
    # main logic
    return cls(written_morse)  # instead of `self.pattern =  written_morse`.

Lastly, I see that you used square brackets with the .split method. It's probably a typo, but you should use parentheses instead:

...
def from_string(cls, spoken_morse):
    spoken_morse = spoken_morse.split("-")  # instead of .split["-"]
...
Gerald Wells
Gerald Wells
12,763 Points

its an undersore not a hyphen

Kip Yin
Kip Yin
4,847 Points

What is?

Gerald Wells
Gerald Wells
12,763 Points

Look at the challenge

Kip Yin
Kip Yin
4,847 Points

I did. I don't understand what "it" is referring to.

Kip Yin
Kip Yin
4,847 Points

You mean .split("-")?

Gerald Wells
Gerald Wells
12,763 Points

I misread your code, I am a moron. disreguard

ashleytan
ashleytan
6,131 Points

Thank you for the detailed and clear response!

Gerald Wells
Gerald Wells
12,763 Points
Gerald Wells
Gerald Wells
12,763 Points

It appears as though you didn't watch the video previous to the challenge... you should probably go back through it; your syntax for @classmethod is careless. Here is the answer but I am not really helping you with the solution. I purposely made an obscure solution so hopefully you will go back and take the time to comprehend Kenneth Love's video.

@classmethod
def from_string(cls, string):
    char = {"dash": "_", "dot": "."}
    pattern=[c for i in list(map(lambda k: char[k], string.split("-"))) for c in i]
    return cls(pattern)
ashleytan
ashleytan
6,131 Points

I didn't realise I completely missed a video! I went back to watch it and now everything is clear. Thanks.