I need a function that turns a list like [10,5,2,3,7] to a list like [4,2,0,1,3]
Basically a list [0,1,2,3,4...] but arranged in the order that the original list has, smallest to biggest.
I have no idea where to even start on a function like this. I have Python 3.5.2.
This solution would work; however, there is probably a solution that is more space efficient. This solution does allow for repeat elements though.
l1 = [10, 5, 2, 3, 7] # Your list
l2 = sorted(l1) # Get the sorted version of our list.
# A dictionary containing each element and a list of the indices where they are found
element_indices = {}
for index, element in enumerate(l2):
if element not in element_indices:
element_indices[element] = [index] # Store the index for each element when it is sorted
else: # We have seen this element before
element_indices[element].append(index)
l2 = [element_indices[value].pop() for value in l1] # Change each element to its sorted equivalent index
print(l2) # [4, 2, 0, 1, 3]
hiro protagonist's answer was close, but he indexed the wrong list.
>>> data = [10,5,2,3,7]
>>> sorted_list = sorted(data)
>>> [sorted_list.index(item) for item in data]
[4, 2, 0, 1, 3]
This wouldn't account for cases where you want to account for multiple occurrences and whatnot, but I'm not sure if that's required in your case.
Try this:
>>> d = [10, 5, 2, 3, 7]
>>> [sorted(d).index(i) for i in d]
[4, 2, 0, 1, 3]
