Game Development Reference
In-Depth Information
10 - Tic Tac Toe
When you alter the list that cheese refers to, the list that spam refers to is also changed
because they are the same list. If you want spam and cheese to store two different lists,
you have to create two different lists instead of copying a reference:
>>> spam = [0, 1, 2, 3, 4, 5]
>>> cheese = [0, 1, 2, 3, 4, 5]
In the above example, spam and cheese have two different lists stored in them (even
though these lists are identical in content). Now if you modify one of the lists, it will not
affect the other because spam and cheese have references to two different lists:
>>> spam = [0, 1, 2, 3, 4, 5]
>>> cheese = [0, 1, 2, 3, 4, 5]
>>> cheese[1] = 'Hello!'
>>> spam
[0, 'Hello!', 2, 3, 4, 5]
>>> cheese
[0, 1, 2, 3, 4, 5]
Figure 10-8 shows how the two references point to two different lists:
Figure 10-8: Two variables each storing references to two different lists.
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