compute bias option for file listing NIGHT EXPID to use

bin/desi_compute_bias

@@ -8,13 +8,20 @@ parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFo
 description="Compute a master bias from a set of raw data bias images",
 epilog='''This is simply a median of the input raw images.'''
 )
-parser.add_argument('-i','--image', type = str, default = None, required = True, nargs="*",
+parser.add_argument('-i','--image', type = str, default = None, nargs="*",
                     help = 'path of image fits files')
-parser.add_argument('-o','--outfile', type = str, default = None, required = True,
+parser.add_argument('-o','--outfile', type=str, default = None, required = True,
                     help = 'output median image filename')
 parser.add_argument('--camera',type = str, required = True,
                     help = 'camera name BX,RX,ZX with X from 0 to 9')
+parser.add_argument('--explistfile', type=str, default=None, required=False,
+                    help = 'Read NIGHT EXPID from file (one per line)')
 
 args        = parser.parse_args()
 
-compute_bias_file(args.image, args.outfile, args.camera)
+if (args.image is not None) and (args.explistfile is not None):
+    print('ERROR: specify --image or --explistfile but not both')
+    sys.exit(1)
+
+compute_bias_file(args.image, args.outfile, args.camera,
+                  explistfile=args.explistfile)

py/desispec/ccdcalib.py

@@ -187,17 +187,44 @@ def compute_dark_file(rawfiles, outfile, camera, bias=None, nocosmic=False,
     log.info(f"done")
 
 
-def compute_bias_file(rawfiles, outfile, camera):
+def compute_bias_file(rawfiles, outfile, camera, explistfile=None):
     """
     Compute a bias file from input ZERO rawfiles
 
     Args:
         rawfiles: list of input raw file names
         outfile (str): output filename
         camera (str): camera, e.g. b0, r1, z9
+
+    Options:
+        explistfile: filename with text list of NIGHT EXPID to use
+
+    Notes: explistfile is only used if rawfiles=None; it should have
+    one NIGHT EXPID entry per line.
     """
     log = get_logger()
 
+    if explistfile is not None:
+        if rawfiles is not None:
+            msg = "specify rawfiles or explistfile, but not both"
+            log.error(msg)
+            raise ValueError(msg)
+
+        rawfiles = list()
+        with open(explistfile, 'r') as fx:
+            for line in fx:
+                line = line.strip()
+                if line.startswith('#') or len(line)<2:
+                    continue
+                night, expid = map(int, line.split())
+                filename = io.findfile('raw', night, expid)
+                if not os.path.exists(filename):
+                    msg = f'Missing {filename}'
+                    log.critical(msg)
+                    raise RuntimeError(msg)
+
+                rawfiles.append(filename)
+
     log.info("read images ...")
     images=[]
     shape=None