初始化多维列表后，Python列表分配超出范围

Question

So, I'm trying to work with multidimensional lists to make a map for an ASCII game. I have code to initialize the list,

mapData = [[[0 for m in range(3)] for x in range(32)] for y in range(32)] 

then I try to access and change a value in the variable using this code,

mapData[0][5][5] = 1

and get this error message,

IndexError: list assignment index out of range

I've tried many things, but can't figure anything out.

Answer 1

Your innermost list has only three cells, so trying to access [5] on it won't work.

The indices go from outermost (with 32 entries) to innermost (with 3 entries). If you expected your innermost list to have 6 or more cells, you need to adjust your for m in range(3) loop.

If you expected to index the first cell of the innermost list, perhaps you needed to reverse the indices:

mapData[5][5][0] = 1

To spell it out some more:

• mapData[0] returns the first element of the outermost list, generated by the for y in range(32) loop in your nested list comprehensions.
• [5] in mapData[0][5] then accesses the 6th element of the previous result, a list from the for x in range(32) loop.
• [5] in mapData[0][5][5] tries to index the innermost list, one of the list objects generated by [0 for m in range(3)] . Because those lists only have 3 0 values each, an IndexError exception is raised.