Thank you to both of you for this explanatin. I'm coming from the fortran world and so I never had to deal with this before...
Sorry to have polluate the list for a stupid things Thanks again that clarify the problem Nicolas Le Thursday 08 February 2007 17:01:36 Travis Oliphant, vous avez écrit : > [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 > > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
