Python: Sorting y value array according to ascending x array

Question

If I had two arrays of the form:

x = [0, 7, 2, 4, 6, 9, 5]

y = [1, 2, 3, 4, 5, 6, 7]

i.e., I have data points at [0,1], [3,2], [x_n,y_n] etc. How would I organise y for a corresonding ascending x value? In other words I end up with ascending values of x:

x = [0, 2, 4, 5, 6, 7, 9]

Matched to their corresponding y values:

y = [1, 3, 4, 7, 5, 2, 6]

I'm guessing I would need to stitch the two arrays together then sort according to x, but I'm not quite sure of the exact syntax for this. Any helps would be greatly appreciated.

Answer 1

I would use zip with a lambda:

In [55]: x = [0, 7, 2, 4, 6, 9, 5]

In [56]: y = [1, 2, 3, 4, 5, 6, 7]

In [57]: L = sorted(zip(x,y), key=operator.itemgetter(0))

In [58]: new_x, new_y = zip(*L)

In [59]: new_x
Out[59]: (0, 2, 4, 5, 6, 7, 9)

In [60]: new_y
Out[60]: (1, 3, 4, 7, 5, 2, 6)

Don't forget to import operator

Answer 2

You can sorted them as tuples after you zip them

>>> sorted((i,j) for i,j in zip(x,y))
[(0, 1), (2, 3), (4, 4), (5, 7), (6, 5), (7, 2), (9, 6)]

To iterate over these pairs, you could do something like

sorted_pairs = sorted((i,j) for i,j in zip(x,y))
for i,j in sorted_pairs:
    # do something with each i and j value, which are x and y respectively

Or you can index directly like

sorted_pairs[0][0]  # x of the first tuple
sorted_pairs[0][1]  # y of the first tuple
sorted_pairs[3][0]  # x of the fourth tuple... etc