how to copy an array into a bigger array(partial copy)

Question

I am trying to copy an array into another.

a = np.array([1]*3)
b = np.array([2]*2)

I tried copyto()

np.copyto(a,b)

But I get:

Traceback (most recent call last): File "", line 1, in np.copyto(a,b) ValueError: could not broadcast input array from shape (2) into shape (3)

How can I get a to become equal to [2,2,1] ?

Answer 1

Assign the values in b to a slice of a:

In [16]: a[:len(b)] = b

In [17]: a
Out[17]: array([2, 2, 1])