If I have a nested array lets say:
arr = [[1, 2, 3, 4], [5, 6, 7, 8]]
I want to divide element wise so my output would be:
[5/1, 6/2, 7/3, 8/4]
Just using fractions to be clear on what I'm asking.
2 Answers
Try to use the zip() function:
d=[] #This is done to avoid name 'd' is not defined
arr = [[1, 2, 3, 4], [5, 6, 7, 8]]
zipped = zip(arr[1], arr[0])
for i1,i2 in zipped:
d.append(i1/i2)
2 Comments
HydeNor
If you don't want to use zip() you could iterate through the first list with enumerate() and then access the second list with the counter.
You can easily do this with numpy.
Extract the second row, and divide it by the first row element wise:
arr = np.array([[1, 2, 3, 4], [5, 6, 7, 8]])
np.array(arr[1, :] / arr[0, :])
# [5. 3. 2.33333333 2. ]
If instead you want to do it with a for loop:
[arr[1][i] / arr[0][i] for i in range(len(arr[0]))]
2 Comments
QuantumMecha
I've edited my post to show a for loop approach as well, or I would use @luigigi's approach
[b/a for a,b in zip(*arr)]