concatenating arrays in python like matlab without knowing the size of the output array

I am trying to concatenate arrays in python similar to matlab

array1= zeros(3,500);
array2=ones(3,700);
array=[array1, array2];

I did the following in python:

array1=np.zeros((3,500))
array2=np.ones((3,700))
array=numpy.concatenate((array1, array2), axis=2)

however this gives me different results when i access try to “array[0,:]”
is there a way in python to put arrays in one array similar to matlab.

Thank you