Concatenate several np arrays in python

concatenate can accept a sequence of array-likes, such as args:

In [11]: args = (x1, x2, x3)

In [12]: xt = np.concatenate(args)

In [13]: xt
Out[13]: array([1, 0, 1, 0, 0, 1, 1, 1, 1])

By the way, although axis=1 works, the inputs are all 1-dimensional arrays (so they only have a 0-axis). So it makes more sense to use axis=0 or omit axis entirely since the default is axis=0.