On Fri, Aug 19, 2011 at 9:23 AM, Warren Weckesser <warren.weckes...@enthought.com> wrote: > > > On Fri, Aug 19, 2011 at 10:09 AM, Jeremy Conlin <jlcon...@gmail.com> wrote: >> >> On Fri, Aug 19, 2011 at 8:01 AM, Brent Pedersen <bpede...@gmail.com> >> wrote: >> > On Fri, Aug 19, 2011 at 7:29 AM, Jeremy Conlin <jlcon...@gmail.com> >> > wrote: >> >> On Fri, Aug 19, 2011 at 7:19 AM, Pauli Virtanen <p...@iki.fi> wrote: >> >>> Fri, 19 Aug 2011 07:00:31 -0600, Jeremy Conlin wrote: >> >>>> I would like to use numpy's memmap on some data files I have. The >> >>>> first >> >>>> 12 or so lines of the files contain text (header information) and the >> >>>> remainder has the numerical data. Is there a way I can tell memmap to >> >>>> skip a specified number of lines instead of a number of bytes? >> >>> >> >>> First use standard Python I/O functions to determine the number of >> >>> bytes to skip at the beginning and the number of data items. Then pass >> >>> in `offset` and `shape` parameters to numpy.memmap. >> >> >> >> Thanks for that suggestion. However, I'm unfamiliar with the I/O >> >> functions you are referring to. Can you point me to do the >> >> documentation? >> >> >> >> Thanks again, >> >> Jeremy >> >> _______________________________________________ >> >> NumPy-Discussion mailing list >> >> NumPy-Discussion@scipy.org >> >> http://mail.scipy.org/mailman/listinfo/numpy-discussion >> >> >> > >> > this might get you started: >> > >> > >> > import numpy as np >> > >> > # make some fake data with 12 header lines. >> > with open('test.mm', 'w') as fhw: >> > print >> fhw, "\n".join('header' for i in range(12)) >> > np.arange(100, dtype=np.uint).tofile(fhw) >> > >> > # use normal python io to determine of offset after 12 lines. >> > with open('test.mm') as fhr: >> > for i in range(12): fhr.readline() >> > offset = fhr.tell() >> > >> > # use the offset in your call to np.memmap. >> > a = np.memmap('test.mm', mode='r', dtype=np.uint, offset=offset) >> >> Thanks, that looks good. I tried it, but it doesn't get the correct >> data. I really don't understand what is going on. A simple code and >> sample data is attached if anyone has a chance to look at it. > > > Your data file is all text. memmap is generally for binary data; it won't > work with this file. > > Warren
Yikes! I missed the "binary" in the first line of the documentation. Sorry! Jeremy _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
