How to print column in python array?

Question

I have an array of 3 numbers per row, 4 columns deep. I am struggling to figure out how I can write the code to print all numbers from a specified column rather than from a row.

I have searched for tutorials that explain this easily and just cannot find any that have helped. Can anyone point me in the right direction?

Answer 1

If you're thinking of python lists as rows and columns, probably better to use numpy arrays (if you're not already). Then you can print the various rows and columns easily, E.g.

import numpy as np
a = np.array([[1,2,6],[4,5,8],[8,3,5],[6,5,4]])
#Print first column
print(a[:,0])
#Print second row
print(a[1,:])

Note that otherwise you have a list of lists and you'd need to use something like,

b = [[1,2,6],[4,5,8],[8,3,5],[6,5,4]]
print([i[0] for i in b])

Answer 2

You can do this:

>>> a = [[1,2,3],[1,1,1],[2,1,1],[4,1,2]]
>>> print [row[0] for row in a]
[1, 1, 2, 4]