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Actually, all file operations behave the same (well, all: I tried one: readline():-): they behave as if the whole file has been read. I.e. file.readline() within a "for line in file" will return an empty string.

If a file iterator behaves as if it has read the complete file at once on instantiation (never mind what it actually does: if it *behaves* as if this happens) I think this should just be documented and that's it.