On Mon, Sep 24, 2012 at 4:14 PM, Chris Angelico <ros...@gmail.com> wrote: > file.pos = 42 # Okay, you're at position 42 > file.pos -= 10 # That should put you at position 32 > foo = file.pos # Presumably foo is the integer 32 > file.pos -= 100 # What should this do?
Since ints are immutable, the language specifies that it should be the equivalent of "file.pos = file.pos - 100", so it should set the file pointer to 68 bytes before EOF. > foo -= 100 # But this sets foo to the integer -68 > file.pos = foo # And this would set the file pointer 68 bytes from > end-of-file. Which is the same result. > I don't see it making sense for "file.pos -= 100" to suddenly put you > near the end of the file; it should either cap and put you at position > 0, or do what file.seek(-100,1) would do and throw an exception. I agree, but the language doesn't allow those semantics. Also, what about the use of `f.seek(0, os.SEEK_END)` to seek to EOF? I'm not certain what the use cases are, but a quick google reveals that this does happen in real code. If a pos of 0 means BOF, and a pos of -1 means 1 byte before EOF, then how do you seek to EOF without knowing the file length? -- http://mail.python.org/mailman/listinfo/python-list
