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Re: is != == (Re: [pygame] Sticky Variables: Terrain Loading)

Heh, so much for "there's only one way to do it in python".  We have:

y = [x[1], x[2], ..., x[n]]
y = list(x)
y = x[:]
y = deepcopy(x) # slightly different

and I would have said

y = [z for z in x]

I think of these, y = list(x) is probably the "right" way.

--Mike

Kevin wrote:
I remember having issues at one point with references as I was confused at why changes to one array changed the other. My work-around has simply been: 
x = [1, 2, 3]
y = x[:]

Nice to see there are other methods though.
On Wed, Mar 12, 2008 at 9:04 PM, Greg Ewing <greg.ewing@xxxxxxxxxxxxxxxx <mailto:greg.ewing@xxxxxxxxxxxxxxxx>> wrote: 

    Ian Mallett wrote:

    > If I have something like:
    > x = [1,2,3,4,5,6]
    > y = x
    > then changes to y change x.

    That's a rather loose way of talking about it. What's
    happening is that x and y refer to the same object,
    so any changes made to that object will be seen through
    both x and y.

    The important things to understand are:

    (1) Python variables always contain references to objects,
        not the objects themselves.

    (2) The '=' operation is always reference assignment.
        It never copies any objects.

    > y = [x[0],x[1],x[2],x[3],x[4],x[5]]
    > ...which doesn't change x when y is changed.

    Also

    (3) The [...] notation always constructs a new list
        object.

    --
    Greg




--
This, from Jach.

How many programmers does it take to change a light bulb?
None. It's a hardware problem.

How many Microsoft programmers does it take to change a light bulb?
None. Microsoft just declared darkness as the newest innovation in cutting-edge technology.