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Python

Posted by Denis Chernenko
Denis Chernenko
4,077 Points

No method named `from_string`

please advice what i've done wrong

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)


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

    @classmethod

    def from_string(cls, string):
        corr = []
        new_string = []
        new_string =string.split("-")
        for i in new_string:
            if i == "dot":
                corr.append(".")
            else:
                corr.append("_")
        return corr

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,423 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

You have the right idea, but are missing a key element of the task

  • The method from_string should be a classmethod of Letter, not S
  • The method should return a new instance with the correct pattern (['_', '.']).
  • Instead of return corr return cls(pattern=corr)

Post back if you need more help. Good luck!!

Suraj Shah
Suraj Shah
1,055 Points
Suraj Shah
Suraj Shah
1,055 Points

Hi Chris,

This gave me some good steer but I had follow up questions:

what is the logic behind return cls(pattern=corr). I think I don't understand how the return cls works, therefore I cannot understand why you would equate pattern = cord

I have the following code:

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)

    @classmethod
    def from_string(cls, text):
        convert_to_list = text.split(-)
        reformatted = []
        for item in convert_to_list:
            if item == "dash":
                reformatted.append(".")
            elif item == "dot":
                reformatted.append("_")
            else:
                continue
        return cls(pattern = reformatted)

[MOD: fixed ```python formatting -cf]

Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

The pattern cls(pattern=reformatted) says:

  • "cls" is the class cls passed to the classmethod. As a class, it can be called like a function to create a new instance of that class
  • "pattern=reformatted" is the argument list to be used by cls.__init__ to create the new instance.