how to select particular rows data from a array

[raady07]

I am new programmer to python. 
I have a text file having 360 rows and 190 columns of data. 
In matlab, if I load the text file and x_data will be variable of size 360x190 columns.
If I want to select 1 to 20 , 46 to 65, ... rows of data , I simply give 
x_data_train = xdata([1:20,46:65,91:110,136:155,181:200,226:245,271:290,316:335], :);
the resulting x_data_train will be the array of my desired. 

How can do that in python ? 

x_data = np.loadtxt('dataset_300mm.txt', unpack=True)
x_data_train = []
x_data_train.append(x_data[1:20],
                   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])

if I do using append operation , the resultant of the array is strange , it is array of 8 subsets of array for 20*192, but I want it to be one array 160*192