Growing matrices columnwise in NumPy

Question

In pure Python you can grow matrices column by column pretty easily:

data = []
for i in something:
    newColumn = getColumnDataAsList(i)
    data.append(newColu         


        

Answer 1

Usually you don't keep resizing a NumPy array when you create it. What don't you like about your third solution? If it's a very large matrix/array, then it might be worth allocating the array before you start assigning its values:

x = len(something)
y = getColumnDataAsNumpyArray.someLengthProperty

data = numpy.zeros( (x,y) )
for i in something:
   data[i] = getColumnDataAsNumpyArray(i)