Pythonic way to create a numpy array from a list of numpy arrays

Question

I generate a list of one dimensional numpy arrays in a loop and later convert this list to a 2d numpy array. I would\'ve preallocated a 2d numpy array if i knew the number o

Answer 1

I'll add my own version of ~unutbu's answer. Similar to numpy_all_the way, but you dynamically resize if you have an index error. I thought it would have been a little faster for small data sets, but it's a little slower - the bounds checking slows things down too much.

initial_guess = 1000

def my_numpy_all_the_way(k):
    arr=np.empty((initial_guess,M))
    for x,row in enumerate(make_test_data(k)):
        try:
            arr[x]=row
        except IndexError:
            arr.resize((arr.shape[0]*2, arr.shape[1]))
            arr[x]=row
    arr.resize((k,M))
    return arr