On Tue, Sep 25, 2012 at 7:49 AM, Dave Angel <d...@davea.name> wrote: > On 09/24/2012 05:35 PM, zipher wrote: >> Let file-type have an attribute .pos for position. Now you can get rid of >> the seek() and tell() methods and manipulate the file pointer more easily >> with standard arithmetic operations. >> >>>>> file.pos = x0ae1 #move file pointer to an absolute address >>>>> file.pos +=1 #increment the file pointer one byte >>>>> curr_pos = file.pos #read current file pointer > > And what approach would you use for positioning relative to > end-of-file? That's currently done with an optional second parameter to > seek() method.
Presumably the same way you reference a list element relative to end-of-list: negative numbers. However, this starts to feel like magic rather than attribute assignment - it's like manipulating the DOM in JavaScript, you set an attribute and stuff happens. Sure it's legal, but is it right? Also, it makes bounds checking awkward: 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? 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. 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. But doing the exact same operation on a saved snapshot of the position and reassigning it would then have quite different semantics in an unusual case, while still appearing identical in the normal case. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
