[...] > So finally here's my question: If you are using data.append(), doesn't > that just put all the numbers into one long list?
no, append appends extend does what you think How are the tuples > still being created in this case so that the list comprehensions still > work? It seems like there is no longer any 'row' to refer to in data. why not to fire interpreter to see what happens >>> line1 = "1 2 3 4" >>> line2 = "5 6 7 8" >>> lst = [] >>> lst.append(map(float, line1.split())) >>> lst [[1.0, 2.0, 3.0, 4.0]] >>> lst.append(map(float, line2.split())) >>> lst [[1.0, 2.0, 3.0, 4.0], [5.0, 6.0, 7.0, 8.0]] >>> hth, Daniel -- http://mail.python.org/mailman/listinfo/python-list
