Python; Append vector to an array

Question

I've got

Xa = [a1,a2,a3]
Xb = [b1,b2,b3]
Xc = [c1,b2,b3]

And I want

X = [[a1,a2,a3],[b1,b2,b3],[c1,b2,b3]]

Im using numpy append, concatenate, hstack, vstack, and others functions, but them doesnt work or gives me this

X = [a1,a2,a3,b1,b2,b3,c1,b2,b3]

Also after this process I will need to append Xd, Xe, Xf and so on, so I need a way to add these vectors to the array as they come.

Any ideas on what Im doing wrong or what to do?

Edit your question to make it clear where you want numpy arrays, and where you are happy with lists. Regarding your use of vstack etc, show us how you used the functions and what was wrong. — hpaulj
– hpaulj, Commented Jul 20, 2015 at 16:44

igauravsehrawat · Accepted Answer · 2015-07-20 16:08:29Z

2

It's pretty simple if just simple array. initialize an empty array and keep appending your arrays to it.

Xa = ['a1','a2','a3']
Xb = ['b1','b2','b3']
Xc = ['c1','b2','b3']

Empty array

resultArray = []
resultArray.append(Xa)
resultArray.append(Xb)
resultArray.append(Xc)

output:

[['a1','a2','a3'], ['b1','b2','b3'], ['c1','b2','b3']]

Hope this helps

Cheers

answered Jul 20, 2015 at 16:08

igauravsehrawat

3,9844 gold badges38 silver badges48 bronze badges

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

3 Comments

hpaulj Over a year ago

You aren't using arrays here, at least not numpy ones. You using Python lists.

igauravsehrawat Over a year ago

@hpaulj OP didn't said he had numpy array. he just mentioned he used various methods. i just took OP code and put the result as he wanted.

hpaulj Over a year ago

The OP was sending mixed signals, showing lists, but tagging the question with numpy and mentioning various numpy functions. As well as talking about arrays and vectors. But since he accepted your answer, that numpy stuff must have been a mistake.

Kasravnd · Accepted Answer · 2015-07-20 16:02:09Z

0

You can use np.vstack :

Xa =np.array(['a1','a2','a3'])
Xb =np.array( ['b1','b2','b3'])
Xc = np.array(['c1','b2','b3'])

>>> np.vstack((Xa,Xb,Xc))
array([['a1', 'a2', 'a3'],
       ['b1', 'b2', 'b3'],
       ['c1', 'b2', 'b3']], 
      dtype='|S2')

answered Jul 20, 2015 at 16:02

Kasravnd

108k19 gold badges167 silver badges195 bronze badges

Collectives™ on Stack Overflow

Python; Append vector to an array

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related