In article <[EMAIL PROTECTED]>, ssecorp <[EMAIL PROTECTED]> wrote:
> >>> def mod(x,y): > return x.append(y) > > >>> mod([1,2],3) > >>> k=[1,2,3] > >>> k > [1, 2, 3] > >>> l = mod(k,4) > >>> l > >>> k > [1, 2, 3, 4] > >>> l > >>> k==l > False > >>> mod(k,5) > >>> k > [1, 2, 3, 4, 5] > >>> mod(l,4) > > Traceback (most recent call last): > File "<pyshell#29>", line 1, in <module> > mod(l,4) > File "<pyshell#18>", line 2, in mod > return x.append(y) > AttributeError: 'NoneType' object has no attribute 'append' > >>> l > >>> l=k > >>> l > [1, 2, 3, 4, 5] > >>> i=mod(k,1) > >>> i > >>> > > same stuff but i dont find this intuitive. You need to read the docs. AList.append(x) does _not_ return AList with x appended. In fact it returns None, because it wants to be a "procedure" that doesn't return anything at all, but there is no such thing in Python; functions and methods that do not explicitly contain a "return" statement return None. So when you say "return x.append(a)" you're saying "return None", which explains the rest of it. You noticed that the second line of > >>> l = mod(k,4) > >>> l didn't print anything? That's because the first line set l to None. If you'd typed "print l" instead of just "l" you would have seen >>> l = mod(k,4) >>> l >>> None -- David C. Ullrich -- http://mail.python.org/mailman/listinfo/python-list
