How to make newlist point to its own memory than that of previous list in python-CodePudding

In python, if we make a list out of an old list, the new list still points to the memory point of old list where the original value is stored. I don't know what this phenomena is called but can I do what I want to do, if so how come (new to programming).

    z=[[1,2,3],[4,5,6],[7,8,9]]
    y=[]
    for i in range(len(z)):
        y.append(z[i])
    
    y[0][0]='A'
    
    print(y)
    print(z)

#Output:
[['A', 2, 3], [4, 5, 6], [7, 8, 9]]
[['A', 2, 3], [4, 5, 6], [7, 8, 9]]

#The Output I want:
[['A', 2, 3], [4, 5, 6], [7, 8, 9]]
[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

CodePudding user response：

As you want to use a new list which point to a new space, you can change your code to this:

    z=[[1,2,3],[4,5,6],[7,8,9]]
    y=[]
    for i in range(len(z)):
        # copy() can return a new list point to a new space, just like the function name.
        y.append(z[i].copy())
    y[0][0]='A'
    
    print(y)
    print(z)