Python get column vector from array of tuples

Question

I have an array of tuples (from prev processing of a structured array, but the filed info was lost).

>>> arr
[(0.109, 0.5), (0.109, 0.55), (0.109, 0.6)]
>>>

I need to extract the column vectors for first and second column.

Using two indices with fixed values works OK, but wildcarding the row fails.

>>> arr[0][1]
0.5
>>> arr[*][1]
  File "<stdin>", line 1
    arr[*][1]
                      ^
SyntaxError: invalid syntax
>>>

Your feedback is appreciated.

Why did you imagine "wildcarding" would work? Just a guess??? Also, are you working with an array or a list, as your output suggests? — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Feb 10, 2018 at 0:56

Ronan Boiteau · Accepted Answer · 2018-02-10 00:49:50Z

6

To get a list that contains the first element of each tuple:

[elem[0] for elem in arr]

...and the second element:

[elem[1] for elem in arr]

answered Feb 10, 2018 at 0:49

Ronan Boiteau

10.3k7 gold badges39 silver badges62 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

jpp · Accepted Answer · 2018-02-10 00:50:37Z

4

You can use numpy for this:

import numpy as np

arr = [(0.109, 0.5), (0.109, 0.55), (0.109, 0.6)]
arr = np.array(arr)

arr[:, 1]  # array([ 0.5 ,  0.55,  0.6 ])
arr[0, :]  # array([ 0.109,  0.5  ])

answered Feb 10, 2018 at 0:50

jpp

166k37 gold badges301 silver badges362 bronze badges

Collectives™ on Stack Overflow

Python get column vector from array of tuples

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related