Converting a list of tuples to an array or other structure that allows easy slicing

Question

Using list comprehension I have created a list of tuples which looks like

temp = [(1, 0, 1, 0, 2), (1, 0, 1, 0, 5), (1, 0, 2, 0, 2), (1, 0, 2, 0, 5)]

I could also create a list of lists if that works easier.

Either way, I would now like to get an array, or a 2D list, from the data. Something where I can easily access the value of the first element in each tuple in the above using slicing, something like

first_elements = temp[:,0]

Answer 1

Use numpy for that type of indexing:

import numpy as np
temp = [(1, 0, 1, 0, 2), (1, 0, 1, 0, 5), (1, 0, 2, 0, 2), (1, 0, 2, 0, 5)]

a = np.array(temp)
a[:, 0]

returns

array([1, 1, 1, 1])

Note: all of your inner lists must be of the same size at for this to work. Otherwise the array constructor will return an array of Python lists.

Answer 2

You can use zip and next to get what you want:

temp = [(1, 0, 1, 0, 2), (1, 0, 1, 0, 5), (1, 0, 2, 0, 2), (1, 0, 2, 0, 5)]
print(next(zip(*temp)))

Returns:

(1, 1, 1, 1)