Python - Two Classes's Variables Are Linked

Question

I noticed this problem in something I was making, and managed to reproduce it in a simpler form.

The problem is that I have two players - both of a Person class - and they each have their own grid. I start off with a global grid variable and assign each Person's grid to that global variable. However, when I change one Person's grid, the other Person's grid changes, too!

Here's the code and output:

Anyone have any suggestions as to why this happens?

EDIT:

I tried the list() suggestion. This worked in one program, but in my main program it didn't do anything.

Players[1].Grid = list(Grid)

Players[0].Grid = list(Grid)

This outputs the same thing when I changed on of the lists.

Post text as text, not pictures of text. – melpomene Feb 18 '17 at 16:07 — melpomene, Feb 18 '17 at 16:07

score 0 · Answer 1 · answered Feb 18 '17 at 16:06

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You're sharing the grid between both objects, so when you change it, they both see it. If you want each to have a copy of it, use list() to make a copy of it.

People[a].grid = list(Grid)

answered Feb 18 '17 at 16:06

Scovetta

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Agree with @Woafer, `deepcopy` is needed for complex objects. – Scovetta Feb 18 '17 at 17:58

score 0 · Accepted Answer · edited May 23 '17 at 11:53

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Although Scovetta's answer did work for the example I provided, the code in which I found the problem actually used a 2-Dimensional list, rather than the 1-Dimensional one in the sample.

I have found out from here that more complex objects need

copy.deepcopy

to copy everything, without being just a reference to the old variable.

edited May 23 '17 at 11:53

Community

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answered Feb 18 '17 at 17:22

Woafer

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Python - Two Classes's Variables Are Linked

2 Answers2