Breaking multi spectrum fits

from pyraf import iraf

def sep_spec(spec, aperture):
    """Separate the multi spectrum in its orders"""

    nslits = int(iraf.imhead(spec, Stdout=1)[0].split(',')[1])
    for i in xrange(1, nslits+1):
        spec_in = spec+'[*,'+str(i)+','+aperture+']'
        if i<10:
            spec_out = './'+spec.split('.fits')[0]+'_000'+str(i)+'.fits'
        else:
            spec_out = './'+spec.split('.fits')[0]+'_00'+str(i)+'.fits'
        iraf.imcopy(spec_in, spec_out)