[[' ']*3]*3 buggy behavior?

[shadowphile]

Running 3.9.x in Jupyter Notebook
I used a shortcut to create 3x3 array, why doesn't it act correctly?

brd=[[' ']*3]*3
b=[[' ',' ',' '],[' ',' ',' '],[' ',' ',' ']]
print(b==brd)  #if these are equivalent, why doesn't the *3 method update correctly?
brd[0][0]='X'
b[0][0]='X'
print(brd)
print(b)

For those not running the code, line 3 prints True but the result of updating a single entry is not correct using the *3 method, here are the outputs:

Output:
[['X', ' ', ' '], ['X', ' ', ' '], ['X', ' ', ' ']]
[['X', ' ', ' '], [' ', ' ', ' '], [' ', ' ', ' ']]

thanks