Numpy array: concatenate arrays and integers

Question

In my Python program I concatenate several integers and an array. It would be intuitive if this would work:

x,y,z = 1,2,np.array([3,3,3])
np.concatenate((x,y,z))

However, instead all ints have to be converted to np.arrays:

x,y,z = 1,2,np.array([3,3,3])
np.concatenate((np.array([x]),np.array([y]),z))

Especially if you have many variables this manual converting is tedious. The problem is that x and y are 0-dimensional arrays, while z is 1-dimensional. Is there any way to do the concatenation without the converting?

Brionius · Accepted Answer · 2013-08-20 11:57:49Z

7

They just have to be sequence objects, not necessarily numpy arrays:

x,y,z = 1,2,np.array([3,3,3])
np.concatenate(([x],[y],z))
# array([1, 2, 3, 4, 5])

Numpy also does have an insert function that will do this:

x,y,z = 1,2,np.array([3,3,3])
np.insert(z, [0,0], [x, y])

I'll add that if you're just trying to add integers to an list, you don't need numpy to do it:

x,y,z = 1,2,[3,3,3]
z = [x] + [y] + z

or

x,y,z = 1,2,[3,3,3]
[x, y] + z

or

x,y,z = 1,2,[3,3,3]
z.insert(0, y)
z.insert(0, x)

edited Aug 20, 2013 at 11:57

answered Aug 20, 2013 at 11:52

Brionius

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1 Comment

Forzaa Over a year ago

Heh, this makes me feel a little bit stupid :). Thanks for your help. Now I also understand that there is a difference between ints/floats and sequence types like lists,tuples etc.

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