title: TypeError: append() missing 1 required positional argument: 'values'
body: <p>I have variable 'x_data' sized 360x190, I am trying to select particular rows of data. </p>
  
  <pre><code> x_data_train = []
   x_data_train = np.append([x_data_train,
                             x_data[0:20,:],
                             x_data[46:65,:],
                             x_data[91:110,:],
                             x_data[136:155,:],
                             x_data[181:200,:],
                             x_data[226:245,:],
                             x_data[271:290,:],
                             x_data[316:335,:]],axis = 0)
  </code></pre>
  
  <p>I get the following error : 
  TypeError: append() missing 1 required positional argument: 'values'</p>
  
  <p>where did I go wrong ?</p>
  
  <p>If I am using </p>
  
  <pre><code>x_data_train = []
  x_data_train.append(x_data[0:20,:])
  x_data_train.append(x_data[46:65,:])
  x_data_train.append(x_data[91:110,:])
  x_data_train.append(x_data[136:155,:])
  x_data_train.append(x_data[181:200,:])
  x_data_train.append(x_data[226:245,:])
  x_data_train.append(x_data[271:290,:])
  x_data_train.append(x_data[316:335,:])
  </code></pre>
  
  <p>the size of the output is 8 instead of 160 rows.</p>
  
  <p>Update: </p>
  
  <p>In matlab, I will load the text file and x_data will be variable having 360 rows and 190 columns.
  If I want to select 1 to 20 , 46 to 65, ... rows of data , I simply give 
  <code>x_data_train = xdata([1:20,46:65,91:110,136:155,181:200,226:245,271:290,316:335], :);</code>
  the resulting x_data_train will be the array of my desired. </p>
  
  <p>How can do that in python because it results array of 8 subsets of array for 20*192 each, but I want it to be one array 160*192</p>