Mikaela LandPython Web Development Techdegree Student 2,324 Points
Slice Functions: Local variable error
In the odds function I keep getting:
UnboundLocalError: local variable 'odds_only' referenced before assignment
Not sure how to fix it. I keep trying to change things around to test it but I've got nothing. I got it to work once but it stopped working the second time.
def first_4(lst): return lst[:4] def first_and_last_4 (lst2): first = lst2 [:4] last = lst2 [-4:] both = first + last return both def odds (num): if len(num) % 2 == 0: odds_only = num [1::2] return odds_only
Alexander Davison65,252 Points
I think you are a bit lost. The
odds function takes in an iterable still, not a number. (It seems that you believe that it takes in an iterable.)
The problem is asking to return an iterable which has all of the odd indexed values from the passed in iterable.
For instance, if I pretended I was within the Python shell:
>>> odds([1, 2, 3, 4, 5]) [2, 4] >>> odds('abcdefg') ['b', 'd', 'f'] >>> odds((1, 2, 3)) 
Here's my solution to this problem:
(Let's call the input iterable
iter and the output iterable
- Go through every number from zero to N-1, where N is
len(iter). Let's call the "current number"
iis odd, add to
iis an index, not the item itself)
Implemented in code, it may look somewhat like this:
def odds(iter): result_iter =  for i in range(len(iter)): if i % 2 != 0: result_iter.append(iter[i]) return result_iter
Simpler way for the Pythonista:
def odds(iter): return [iter[i] for i in range(len(iter)) if i % 2 != 0]
I hope this helps!
Happy coding! ~Alex