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Home/ Questions/Q 6136597
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Editorial Team
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Editorial Team
Asked: May 23, 20262026-05-23T17:37:23+00:00 2026-05-23T17:37:23+00:00

Why this is happening? I don’t really understand: >>> P = [ [()]*3 ]*3

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Why this is happening? I don’t really understand:

>>> P = [ [()]*3 ]*3
>>> P
[[(), (), ()], [(), (), ()], [(), (), ()]]
>>> P[0][0]=1
>>> P
[[1, (), ()], [1, (), ()], [1, (), ()]]
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  1. Editorial Team
    Editorial Team
    2026-05-23T17:37:24+00:00Added an answer on May 23, 2026 at 5:37 pm

    You’ve made 3 references to the same list.

    >>> a = b = []
    >>> a.append(42)
    >>> b
    [42]
    

    You want to do this:

    P = [[()] * 3 for x in range(3)]
    
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