Stack arrays in sequence

Question

I read linewise data from a file and I want to store them in an array.

EDIT: The data cannot be read with loadtxt().

So I do it like this:

data = array([])
for frame in frames:
    # ....
    # get some lines and make some calculations e.g. final result is
    # line = array([1, 2, 3, 4])
    # ....
    if data.size == 0:
        data = line
    else:
        data = vstack( (data, line) )

This works fine, but the if-clausel make the solution just look ugly. I wonder if there is a possibility to get ride of it.

Any ideas?

Answer 1

If the number of elements in line is fixed and you just want to avoid an "ugly" solution, you can do this:

data = []
for f in frames:
    # do your calculation
    # line = [1, 2, 3, 4]
    data += line
data = np.array(data).reshape((-1,4))