In numpy, if I have a vector of zeros like this
vec1 = np.array([0., 0., 0., 0., 0., 0., 0.])
and another one like this vec2 = np.array([1.,2.,3.]), which is the quickest way to obtain
vec3 = np.array([1., 2., 3., 0., 0., 0., 0.])
(Basicaly I want the original vector whose initial entries are filled with the ones of the second vector).
It depends if you want to create a new array or modify in place.
New vec3 array (without altering vec1 and vec2):
vec3 = np.concatenate([vec2, vec1[vec2.shape[0]:]])
or
vec3 = np.r_[vec2, vec1[vec2.shape[0]:]]
Modifying vec1 in place:
vec1[:vec2.shape[0]] = vec2
used input:
vec1 = np.array([0., 0., 0., 0., 0., 0., 0.])
vec2 = np.array([1.,2.,3.])
vec1[:len(vec2)] = vec2