In general you can concatenate a whole sequence of arrays along any axis:
numpy.concatenate( LIST, axis=0 )
but you do have to worry about the shape and dimensionality of each array in the list (for a 2-dimensional 3x5 output, you need to ensure that they are all 2-dimensional n-by-5 arrays already). If you want to concatenate 1-dimensional arrays as the rows of a 2-dimensional output, you need to expand their dimensionality.
As Jorge's answer points out, there is also the function
stack, introduced in numpy 1.10:
numpy.stack( LIST, axis=0 )
This takes the complementary approach: it creates a new view of each input array and adds an extra dimension (in this case, on the left, so each
n-element 1D array becomes a 1-by-
n 2D array) before concatenating. It will only work if all the input arrays have the same shape—even along the axis of concatenation.
vstack (or equivalently
row_stack) is often an easier-to-use solution because it will take a sequence of 1- and/or 2-dimensional arrays and expand the dimensionality automatically where necessary and only where necessary, before concatenating the whole list together. Where a new dimension is required, it is added on the left. Again, you can concatenate a whole list at once without needing to iterate:
numpy.vstack( LIST )
This flexible behavior is also exhibited by the syntactic shortcut
numpy.r_[ array1, ...., arrayN ] (note the square brackets). This is good for concatenating a few explicitly-named arrays but is no good for your situation because this syntax will not accept a sequence of arrays, like your
There is also an analogous function
column_stack and shortcut
c_[...], for horizontal (column-wise) stacking, as well as an almost -analogous function
hstack—although for some reason the latter is less flexible (it is stricter about input arrays' dimensionality, and tries to concatenate 1-D arrays end-to-end instead of treating them as columns).
Finally, in the specific case of vertical stacking of 1-D arrays, the following also works:
numpy.array( LIST )
...because arrays can be constructed out of a sequence of other arrays, adding a new dimension to the beginning.