I need a code that reverses a list without using both return of reverse(). So it can only modify the inputted list. These are the methods i have tried so far that havent worked:
def reversed(x):
x[::-1]
and
def reverse(x):
in_list = []
for i in range(1, len(x)+1):
x.append(x[-i])
The second code gives me an error of 'name 'x' is not defined'
You could assign x to it's reversed value:
x = x[::-1]
This is the same as your first example although it reassigns the variable.
x[:] = x[::-1]), otherwise you are just rebinding the local name x without affecting the list it originally referred to.
x be assigned to the same value after either approach @chepner? Isn't that the intended result? I could be wrongx would be the only variable at hand.reverse function. If it's the same scope, yes, this is fine.def reverse_list(x):
return x[::-1]
x =[1,2,3,4,5]
y = reverse_list(x)
print(y)
Output: [5, 4, 3, 2, 1]
First, don't do this. Mutating data structures makes your coworkers hate you. But if you must, consider:
def mutate(lst):
backward = lst[::-1]
lst.clear()
lst.extend(backward)
a = [1,2,3,4]
print(a)
print(id(a))
mutate(a)
print(a)
print(id(a))
The mutate function makes a reversed copy of its inputs. Then it clears the contents of the list that was passed in so that it's empty. Finally, it fills that empty list with the reversed copy. This way the original object is mutated in place and retains its original ID.
Alternatively, if you're extremely resource limited and are willing for the code to be slower in exchange for not having to temporarily duplicate the input list, you could swap the first and last items, then the second and second-to-lsat items, and so on until you reach the middle of the list:
def mutate_by_swapping(lst):
last_index = len(lst) - 1
for i in range(len(lst) // 2):
lst[i], lst[last_index - i] = lst[last_index - i], lst[i]
x = ["a", "b", "c", "d","e"]
z = []
for i in range(len(x)):
m = len(x) - i -1
z.insert(i,x[m])
print(z)
Output will be: ['e', 'd', 'c', 'b', 'a']
reversedfunction orreturnstatement?forloop inside thereverse(x)function. So, you need to indent theforloop appropriately.