[Tutor] Question if my reasoning is right

[Darth Kaboda]

I'm questioning my reason for why the follwoing code doesn't behave as I thought it would upon first coding a project.

 

m = 8
n = 10
cb = [[[0, None]] * (n + 1)] * (m + 1)
cb[3][2][0] = 10

 

This last statement causes the every first element in the list to update. Is this becuase this method of initializing a list is just a copy of the same list in memory?

 

To get around this I'm now doing the folowing:

 

m = 8
n = 10
cb = [[[0,None] for x in range(n+1)] for y in range(m+1)]
cb[3][2][0] = 10


This is working by updating only the one list as I want it to. Is this an acceptable practice? Or should I use the standard nested for loops like you'd do in most other languages?

 

Any insight would be greatly appreciated.

 

Thanks,

Brian
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