You can use list comprehension as such:
myfile.txt
:
1 2 3
4 5 6
7 8 9
>>> matrix = open('myfile.txt').read()
>>> matrix = [item.split() for item in matrix.split('\n')[:-1]]
>>> matrix
[['1', '2', '3'], ['4', '5', '6'], ['7', '8', '9']]
>>>
You can also create a function for this:
>>> def matrix(file):
... contents = open(file).read()
... return [item.split() for item in contents.split('\n')[:-1]]
...
>>> matrix('myfile.txt')
[['1', '2', '3'], ['4', '5', '6'], ['7', '8', '9']]
>>>