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Python

Posted by Michael Nanni
Michael Nanni
7,358 Points

How can I test out my code in workspaces?

I've been trying to test this out in the interactive shell from workspaces, but I keep getting errors when trying to import these classes. It's not passing the challenge, but I think I can figure it out once I know how to test it.

What command do I use? 

>>> from morse.py import S                                                     
Traceback (most recent call last):                                             
  File "<stdin>", line 1, in <module>                                          
ModuleNotFoundError: No module named 'morse.py'; 'morse' is not a package

Thanks!

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


class S(Letter):
    def __init__(self):
        pattern = ['.', '.', '.']
        seperator = '-'
        super().__init__(pattern)
        def __str__(self, pattern):           
           for i in pattern:
              if i = '.':
                 pattern[i] = 'dot'
              elif i = '_':
                 pattern[i] = 'dash'
              print(seperator.join(pattern))

3 Answers

KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,971 Points

You see this error message

TypeError: __str__ returned non-string (type NoneType)

because your __str__ method doesn't return anything so print(test) is attempting to print None which is the return value when there is no return statement.

I would have thought you'd have another error first since there should be a colon at the end of this line

def __str__(self)

Some additional comments:

  • You are iterating through self.pattern but then update self.pattern inside the loop with the assignments. It would be better to create a separate list variable before the loop and then append to this list based on your if conditions

  • You have the join syntax reversed. It should be separator.join(list) instead of list.join(separator)

Michael Nanni
Michael Nanni
7,358 Points

That worked! I made some changes based on your comments and managed to pass the challenge. Still the original question remains for me. How can I run this through the shell to get the output I'm returning? 

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

class S(Letter):
    def __init__(self):     
        pattern = ['.', '.', '.']
        super().__init__(pattern)
KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,971 Points
KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,971 Points

pattern is a parameter for __init__ so it doesn't need to be passed in again to __str__. The only parameter needed there is self. Inside the __str__ method you can use it as self.pattern.

Michael Nanni
Michael Nanni
7,358 Points

Hey Kris. I'm getting back to this after a while, but I still seem to be coming across errors in the shell. Maybe I didn't understand your last comment. Hopefully it's something small that I'm just overlooking. Thanks in advance for your help!

In the shell:

>>> from morse import Letter                                                                                 
>>> test = Letter(['.', '.', '.'])                                                                           
>>> print(test)                                                                                              
-                                                                                                            
Traceback (most recent call last):                                                                           
  File "<stdin>", line 1, in <module>                                                                        
TypeError: __str__ returned non-string (type NoneType)                                                       
>>>

And my code:

class Letter: 
    def __init__(self, pattern=None, seperator='-'):
        self.pattern=pattern
        self.seperator=seperator
    def __str__(self)
        for i in self.pattern:
            if i == '.':
                self.pattern = 'dot'
            elif i == '_':
                self.pattern = 'dash'
        print(self.pattern.join(self.seperator))

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

        super().__init__(pattern)
KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,971 Points
KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,971 Points

For the challenge you are to modify class Letter not class S.

I want you to add a __str__ method to the Letter class

Then to test import without the .py extension, create an instance of the class and print.

>>> from morse import Letter                                                         
>>> test = Letter(['.', '.', '.'])                                                   
>>> print(test)

The result should be 

dot-dot-dot
Michael Nanni
Michael Nanni
7,358 Points

Thanks Kris! At first I was getting tab errors with those commands, so I typed it out by hand and that cleared it up. However, now I'm getting a TypeError.

My code

class Letter: 
    def __init__(self, pattern=None):
        self.pattern=pattern
    def __str__(self, pattern):
        for i in pattern:
            if i == '.':
                pattern[i] = 'dot'
            elif i == '_':
                pattern[i] = 'dash'
        print(seperator.join(pattern))

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

In the shell.

>>> from morse import Letter                                                              
>>> test = Letter(['.', '.', '.'])                                                        
>>> print(test)                                                                           
Traceback (most recent call last):                                                        
  File "<stdin>", line 1, in <module>                                                     
TypeError: __str__() missing 1 required positional argument: 'pattern'

What is my method missing there?