Actually all the objects in your list are same, so changing one changes others too:
In [151]: some_list = 4 * [(4 * [0])]
In [152]: [id(x) for x in some_list]
Out[152]: [148641452, 148641452, 148641452, 148641452]
In [160]: some_list[0][1]=5 #you think you changed the list at index 0 here
In [161]: some_list
Out[161]: [[0, 5, 0, 0], [0, 5, 0, 0], [0, 5, 0, 0], [0, 5, 0, 0]] #but all lists are changed
Create your list this way:
In [156]: some_list=[[0]*4 for _ in range(4)]
In [157]: some_list
Out[157]: [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
In [158]: [id(x) for x in some_list]
Out[158]: [148255436, 148695180, 148258380, 148255852]
In [163]: some_list[0][1]=5
In [164]: some_list
Out[164]: [[0, 5, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]] #works fine in this case
