Not really understand why it is not working!

Question

Can someone explain me why it is not working? And what I should do to make it work? 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.

morse.py

class Letter:
    def __init__(self, pattern=None):
        self.pattern = pattern
    def __str__(self, pattern):
        d = []
        for patt in self.pattern:
            if str(patt) == '.':
                d.append('dot')
            elif str(patt) == '_':
                d.append('dash')
        return join,('-', d)





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

Answer 1 · 2018-11-02T23:03:34Z

November 2, 2018 11:03pm

Hi Ernestas,

You have a couple of problems with your __str__ method.

First, you have the wrong method signature. The challenge is expecting you to have a method that can be called like this:

s = S()
str(s)

(This will produce the output: 'dot-dot-dot')
Since str(s) is equivalent to calling s.__str__() we can see that the __str__() method must have self as its only parameter. Because you have a second parameter, pattern, the method would have to be called like this:

s.__str__(s.pattern)

This breaks the str() method which relies on the object's __str__() method being called with no arguments. Thus an attempt to do this:

s = S()
str(s)

will produce this error: TypeError: __str__() missing 1 required positional argument: 'pattern'

Note also that even if the method signature for __str__ worked, you don't actually use the value passed in as pattern. Inside your method you're just using self.pattern which refers to a totally different variable.

Your second error is that you are not using the string method join() correctly. Remember that the syntax for join() is: some_string.join(some_list) where some_string is the string you want between each item and some_list is the list you are joining.

Hope that clears everything up for you.

Cheers,

Alex

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Ernestas Petruoka

Ernestas Petruoka

Not really understand why it is not working!

1 Answer

Alex Koumparos

Alex Koumparos

Ernestas Petruoka

Ernestas Petruoka