If I want a random train/test split, I use the sklearn helper function:
In [1]: from sklearn.model_selection import train_test_split ...: train_test_split
All you need to do is to set the shuffle parameter to False and stratify parameter to None:
In [49]: train_test_split([1,2,3,4,5,6],shuffle = False, stratify = None) Out[49]: [[1, 2, 3, 4], [5, 6]]