[SciPy-User] Python seek argument type

Tom Kuiper kuiper@jpl.nasa....
Wed Apr 14 10:53:31 CDT 2010


Having disgraced myself with a not-to-bright question yesterday, let me 
try again, still on the topic of reading binary files.

While trying to access the last record in the file I got:

     98     new_pos = pos+76*(index-current_index)
     99     print "Moving file index from",pos,"to",new_pos
--> 100     fd.seek(new_pos,0)
    101   buf = fd.read(76)
    102   data = unpack_from("=LLL dddd dddd", buf)

OverflowError: long int too large to convert to int

The argument in question, new_pos, has a value of 2,252,639,972, which 
is slightly too large to be a Python signed int:
math.log(2252639972,2) = 31.068969607366373
and, of course, a Python int is a C long on a 32-bit machine, which is 
the type specified for the first argument of the underlying C fseek command.

Now a 2.1 GB file is not large by modern standards.  I imagine someone 
must have come up with a way to position past the 2 billionth byte in a 
file.  Does anyone know what it is?

Thanks and regards

Tom


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