How to extend a numpy.ndarray

Question

I have run into some problems to extend numpy.ndarry,Is there some ways like the list's extend()?for example:given two arrays ,a=array([1,2,3]),b=array([4]),
want c=array([1,2,3,4])

Answer 1

There're three equivalent ways:

np.concatenate((a,b))
np.hstack((a,b))
np.r_[a,b]

The latter being most cryptic: it abuses the square brackets operator in order to get the most compact representation form.

Answer 2

or you can use hstack. for example

a = np.array([1,2,3])
b = np.array([4])
c = np.hstack([a,b])