Given a list of numbers, I am trying to write a code that finds the difference between consecutive elements. For instance, A = [1, 10, 100, 50, 40]
so the output of the function should be [0, 9, 90, 50, 10]
. Here is what I have so far trying to use recursion:
def deviation(A):
if len(A) < 2:
return
else:
return [abs(A[0]-A[1])] + [deviation(A[1: ])]
The output I get, however, (using the above example of A as the input) is [9, [90, [50, [10, None]]]]
. How do I properly format my brackets? (I've tried guessing and checking but I this is the closest I have gotten) And how do I write this where it subtracts the current element from the previous element without getting an index error for the first element? I still want the first element of the output list to be zero but I do not know how to go about this using recursion and for some reason that seems the best route to me.
To calculate the asymmetric difference in Python lists: Convert the lists to sets. Compute the difference by subtracting one set from the other. Convert the result to a list.
Approach: The solution is to traverse the array and calculate and print the absolute difference of every pair (arr[i], arr[i+1]).
You can do:
[y-x for x, y in zip(A[:-1], A[1:])]
>>> A = [1, 10, 100, 50, 40]
>>> [y-x for x, y in zip(A[:-1], A[1:])]
[9, 90, -50, -10]
Note that the difference will be negative if the right side is smaller, you can easily fix this (If you consider this wrong), I'll leave the solution for you.
Explanation:
The best explanation you can get is simply printing each part of the list comprehension.
A[:-1]
returns the list without the last element: [1, 10, 100, 50]
A[1:]
returns the list without the first element: [10, 100, 50, 40]
zip(A[:-1], A[1:])
returns [(1, 10), (10, 100), (100, 50), (50, 40)]
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