jf...@ms4.hinet.net wrote: Assuming both x and y are lists
x[:] = y replaces the items in x with the items in y while x = y[:] makes a copy of y and binds that to the name x. In both cases x and y remain different lists, but in only in the second case x is rebound. This becomes relevant when initially there are other names bound to x. Compare: >>> z = x = [1, 2] >>> y = [10, 20, 30] >>> x[:] = y # replace the values, z affected >>> z [10, 20, 30] >>> z = x = [1, 2] >>> y = [10, 20, 30] >>> x = y[:] # rebind. x and z are now different lists >>> z [1, 2] -- https://mail.python.org/mailman/listinfo/python-list
