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Noah Harness
1,383 Pointsslice; iterate backward to get evens in new list
def reverse_evens(iterable): iterable = list(range(10)) return iterable[::-2]
def first_4(iterable):
return iterable[0:4]
def first_and_last_4(iterable):
return iterable[:4] + iterable[-4::1]
def odds(iterable):
return iterable[1::2]
def reverse_evens(iterable):
iterable = list(range(10))
return iterable[::-2]
4 Answers
Steven Parker
230,274 PointsHere's a few hints:
- you must work with the iterable passed in, so do not assign it to something in the function!
- you might calculate which item to start with based on the length of the iterable
- another way would be to select even-indexed items with one slice, then use another slice to get the reverse
Christopher Shaw
Python Web Development Techdegree Graduate 58,248 PointsI had a different solution that did not require enumerate:
Basically takes the modulus of the length of the iterable divided by 2. This will be 0 for an even length or 1 for an odd length and added this value to -2 to make the start. So even length itrables started at -2, while odd length ones started at -1.
def reverse_evens(item):
return item[-2+len(item)%2::-2]
Steven Parker
230,274 PointsThat's exactly what I meant in my second hint. Good job!
ASHOK Gudivada
11,701 Pointsgreat thank Christopher Shaw
Alexander Davison
65,469 PointsThere's two important mistakes:
- You shouldn't set the value of the
iterableparameter in the function. Like the other functions you created, you just take input and you don't change the input. - You function will work for a list with an even amount of elements, but it won't work for a list that has an odd amount of items. If the list has an odd item of items, it will return all odd indices.
To fix both issues, you can do:
- Remove the first line of code after the function definition for
reverse_evens. This line code is disturbing the input. - Change the
return iterable[::-2]line of code to a for loop that adds the element to a new list if the index is even.
Hint 1: You have to start with something like this...
def reverse_evens(iterable):
result_list = []
for idx, item in enumerate(iterable):
# Figure out what goes here...
return result_list
Hint 2: To see if a number is even, you can use this (where n is the number you want to see if it's even): n % 2 == 0
The n % 2 == 0 code will return True if n is even or if it's odd it will return False.
If you need additional hints or you don't understand what I'm saying, please post below :)
I hope this helps. ~Alex
fahad lashari
7,693 PointsHi I tried this method but it doesn't seem to be working. Can you have a look at my code and give additional clues?
def first_4(string):
return string[:4]
def first_and_last_4(string):
return string[:4] + string[-4::1]
def odds(string):
return string[1::2]
def reverse_evens(string): #problem is with function
result = []
for i, j in enumerate(string):
if i % 2 == 0:
result.append(j)
return result
EDIT:
found my stupid mistake. Thanks a bunch!
return result[::-1]
Damian Dabrowski
16,804 PointsI have used modulus to solve reverse_evens function:
def reverse_evens(item):
if len(item)%2 == 0:
return item[-2::-2]
else:
return item[::-2]
Alexander Davison
65,469 PointsAlexander Davison
65,469 PointsAnswered at the same time
Hahaha
Steven Parker
230,274 PointsSteven Parker
230,274 PointsYea, but you get the prize
for verbosity. 