I'm extracting extensions from a multi-extension FITS file, manipulate the data, and save the data (with the extension's header information) to a new FITS file.
To my knowledge pyfits.writeto() does the task. However, when I give it a data parameter in the form of an array, it gives me the error:
'AttributeError: 'numpy.ndarray' object has no attribute 'lower''
Here is a sample of my code:
'file = 'hst_11166_54_wfc3_ir_f110w_drz.fits'
hdulist = pyfits.open(dir + file)'
sci = hdulist[1].data # science image data
exp = hdulist[5].data # exposure time data
sci = sci*exp # converts electrons/second to electrons
file = 'test_counts.fits'
hdulist.writeto(file,sci,clobber=True)
hdulist.close()
I appreciate any help with this. Thanks in advance.
You're confusing the HDUList.writeto method, and the writeto function.
What you're calling is a method on the HDUList object that is returned when you call pyfits.open. You can think of this object as something like a file handle to your original drizzled FITS file. You can manipulate this object in place and either write it out to a new file or save updates in place (if you open the file in mode='update').
The writeto function on the other hand is not tied to any existing file. It's just a high-level function for writing an array out to a file. In your example you could write your array of electron counts out like:
pyfits.writeto(filename, data)
This will create a single-HDU FITS file with the array data in the PRIMARY HDU.
Do be aware of the admonishment at the top of this section of the docs: http://docs.astropy.org/en/v1.0.3/io/fits/index.html#convenience-functions
The functions like pyfits.writeto are there for convenience in interactive work, but are not recommendable for use in code that will be run repeatedly, as in a script. Instead have a look at these instructions to start.