Thread: PySAC

Started: 2009-08-19 00:46:57
Last activity: 2009-08-20 03:04:41
Topics: SAC Help
Norman Heckscher
2009-08-19 00:46:57
Hello everybody,

I have read that there exists a set of Python functions which allow
easy access to SAC files. After some extensive googling I have been
unable to locate anything other than a mention in the following
article: http://adsabs.harvard.edu/abs/2004AGUFM.S21A0273H

Can someone please point me in the correct direction so that I don't
spend time duplicating code?

TIA

Norman.

  • Sebastian Heimann
    2009-08-20 03:04:41
    Hi Norman,

    I have read that there exists a set of Python functions which allow
    easy access to SAC files. After some extensive googling I have been
    unable to locate anything other than a mention in the following
    article: http://adsabs.harvard.edu/abs/2004AGUFM.S21A0273H

    Can someone please point me in the correct direction so that I don't
    spend time duplicating code?

    I also stumbled over that article and couldn't find any other mention of this
    code, that's why I wrote my own module: here it is. It's not very sophisticated
    and also not much tested so far, so be prepared for surprises. It can only do IO
    on binary SAC files.

    Usage is like this:

    import pysacio

    Read a SAC file:

    sac = pysacio.SacFile('test.sac')

    Access header values (assignment is also fine):

    sac.delta
    0.5

    Access the data: it is returned as a NumPy array:

    sac.data[0]
    array([ 0., 0., 1., 2., 0.], dtype=float32)

    To simplify dealing with the reference time of the SAC file, I implemented this:

    sac.get_ref_time()
    Traceback (most recent call last):
    File "<stdin>", line 1, in ?
    File "/bonus/lib/python2.4/site-packages/pysacio.py", line 64, in get_ref_time
    raise SacError('Not all header values for reference time are set.')
    pysacio.SacError: Not all header values for reference time are set.


    ... aaah, OK, the time headers were not set in this file, so let's set them to
    the current system time, for the demo:

    import time
    sac.set_ref_time(time.time())
    sac.get_ref_time()
    1250703611.993
    sac.nzyear
    2009
    sac.nzjday
    231
    sac.nzhour
    17

    You can 'print' the SAC object:

    print sac
    delta: 0.5
    b: 0.0
    e: 2.0
    nzyear: 2009
    nzjday: 231
    nzhour: 17
    nzmin: 40
    nzsec: 11
    nzmsec: 993
    nvhdr: 6
    npts: 5
    iftype: 1
    leven: 1
    lpspol: 0
    lovrok: 1
    lcalda: 1
    unused17: 0
    kevnm: -12345 -12345


    And to write it to file:

    sac.write('newfile.sac')



    Happy coding!

    Sebastian

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