Jerzy Karczmarczuk wrote: > Gurus, before I am tempted to signal this as a bug, perhaps > you might convince me that it should be so. If I type > > l=range(4) > l.extend([1,2]) > > l gives [0,1,2,3,1,2], what else... > > On the other hand, try > > p=range(4).extend([1,2]) > > Then, p HAS NO VALUE (NoneType). > > With append the behaviour is similar. I didn't try other methods, but > I suspect that it won't improve. > > WHY?
.append(), .extend(), .sort() (as well as .update() for dictionaries) all are methods whose *only* effect is to modify the object in-place. They return None as a reminder that they do modify the object instead of copying the object and then modifying the copy. From the FAQ[1] with respect to .sort(): """This way, you won't be fooled into accidentally overwriting a list when you need a sorted copy but also need to keep the unsorted version around.""" [1] http://www.python.org/doc/faq/general.html#why-doesn-t-list-sort-return-the-sorted-list -- Robert Kern [EMAIL PROTECTED] "In the fields of hell where the grass grows high Are the graves of dreams allowed to die." -- Richard Harter -- http://mail.python.org/mailman/listinfo/python-list
