[EMAIL PROTECTED] wrote:
>I have a big problem with numpy, numarray and Numeric (all version)
>
>If I'm using the script at the bottom, I obtain these results:
>
>var1 before function is [3 4 5]
>var2 before function is 1
>var1 after function must be [3 4 5] is [ 9 12 15] <------ problem
>var2 after function must be 1 is 1
>var3 must be the [9 12 15] is [ 9 12 15]
>var4 must be the 'toto' is toto
>
>
>I'm very surprised by the line noted. I always thinking that the input
>variable didn't change the variable itself outside the function.
>
To save yourself confusion, you need to understand the difference
between mutable and immutable types. Mutable types can be changed
inside of a function call.
You also need to understand that = is a "name-binding operation only"
it does not change objects.
>Is it normal and so do I have to do a copy of the input data each time I'm
>calling a function?
>
>
Yes, it's very normal, if your function does an "in-place" operation on
a mutable type.
Consider the following code:
def test(var1, var2):
var1[0] *= 3 # this accesses the 0'th element of var1 and alters it.
var2 = 'toto' # this makes a new object and names it with var2
# whatever was passed in is gone
return var1, var2
test([1,2,3],[1,2])
will return
[3,2,3], 'toto'
-Travis
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