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Python Functional Python Functional Workhorses Map

Posted by Ethan Chae
Ethan Chae
18,747 Points

Map task, Functional Python

What could be wrong with this code? I feel like I'm asking all the petty questions haha but I'm studying all by myself so it's kind of hard.

from copy import copy

backwards = [
    'tac',
    'esuoheerT',
    'htenneK',
    [5, 4, 3, 2, 1],
]

def reverse(iterable):
    iterable = copy(iterable)
    iterable.reverse()
    return  iterable

forwards = list(map(reverse, backwards))

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,457 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,457 Points

The issue is a str object does not have a reverse() method. When the map runs the following error is thrown:

/home/chrisf/Devel/Treehouse/questions/ethan-chae/map-2.py in <module>()
     13     iterable.reverse()
     14     return iterable
---> 15 
     16 forwards = list(map(reverse, backwards))

/home/chrisf/Devel/Treehouse/questions/ethan-chae/map-2.py in reverse(iterable)
     10 
     11 def reverse(iterable):
---> 12     iterable = copy(iterable)
     13     iterable.reverse()
     14     return iterable

AttributeError: 'str' object has no attribute 'reverse'

Note: The line numbers above are shown one higher than your code due to an extra line added above the function def

You will need to rewrite your reverse function to work for both strings and lists. HINT: look at using a slice to reverse the iterable: iterable[::-1]

Also note Task 2 is looking for a map object, not the list returned by applying the map. Your Task 2 answer can be changed to:

forwards = map(reverse, backwards)
Ethan Chae
Ethan Chae
18,747 Points

Thank you Chris! Yeah, I was first thinking about slicing. Then the code passed using just reverse() function, so I just carried on. It worked :)