title: Numpy hstack gives a positional argument error
body: <p>I'm writing a code where I'm trying to add a column of ones to a numpy matrix (X). The following is the line that throws an error:</p>
  <p><code>self.X = np.hstack((np.ones((self.X.shape[0],1)), self.X))</code></p>
  <p>The error I get is the following, even though I have passed a single tuple as an argument within np.hstack :</p>
  <blockquote>
  <p>TypeError: _vhstack_dispatcher() takes 1 positional argument but 2 were given</p>
  </blockquote>