fix: handle instrument param input correctly

GSASII/GSASIIscriptable.py

@@ -588,13 +588,36 @@ def load_pwd_from_reader(reader, instprm, existingnames=[],bank=None):
     HistName = 'PWDR ' + G2obj.StripUnicode(reader.idstring, '_')
     HistName = G2obj.MakeUniqueLabel(HistName, existingnames)
 
-    try:
-        Iparm1, Iparm2 = instprm
-    except ValueError:
+    # get instrumental parameters from reader...
+    if instprm is None:
+        try:
+            Iparm1, Iparm2 = reader.pwdparms['Instrument Parameters']
+            print('Instrument parameters supplied in data file')
+        except KeyError as err:
+            Iparm1 = None  # signal error rather than raise exception inside an exception handler
+        if Iparm1 is None:
+            msg  = "The data file does not have any instrument params associated with it and none were provided."
+            raise Exception(msg)
+
+    # ...or from a file...
+    elif isinstance(instprm, str):
         Iparm1, Iparm2 = load_iprms(instprm, reader, bank=bank)
         G2fil.G2Print('Instrument parameters read:',reader.instmsg)
-    except TypeError:  # instprm is None, get iparms from reader
-        Iparm1, Iparm2 = reader.pwdparms['Instrument Parameters']
+
+    # ...or from an input...
+    elif (
+        isinstance(instprm, (list, tuple)) 
+        and len(instprm) == 2 
+        and all(isinstance(i, dict) for i in instprm)
+        ):
+            Iparm1, Iparm2 = instprm
+            print('Instrument parameters supplied in script')
+
+    # ...else raise an error.
+    else:
+        msg = f"load_pwd... Error: Invalid instprm entered ({instprm!r})"
+        raise Exception(msg)
+
 
     if 'T' in Iparm1['Type'][0]:
         if not reader.clockWd and reader.GSAS:
@@ -1058,14 +1081,20 @@ def add_powder_histogram(self, datafile, iparams=None, phases=[],
         if not multiple: pwdrreaders = pwdrreaders[0:1]
         histlist = []
         if URL:
-            iparmfile = downloadFile(iparams)
-        else:
+            instprm = downloadFile(iparams)
+        elif iparams:
             try:
-                iparmfile = os.path.abspath(os.path.expanduser(iparams))
-            except:
-                pass
+                instprm = os.path.abspath(os.path.expanduser(iparams))
+            except TypeError: # iparams is not a file path
+                if isinstance(iparams, (list, tuple)):
+                    instprm = iparams
+                else:
+                    raise Exception(f"add_powder_histogram Error: Invalid iparams supplied ({iparams!r})")
+        else:
+            instprm = None # will error out unless the reader supplies them
+
         for r in pwdrreaders:
-            histname, new_names, pwdrdata = load_pwd_from_reader(r, iparmfile,
+            histname, new_names, pwdrdata = load_pwd_from_reader(r, instprm,
                                           [h.name for h in self.histograms()],bank=instbank)
             if histname in self.data:
                 G2fil.G2Print("Warning - redefining histogram", histname)

docs/source/GSASIIscriptable.rst

@@ -1664,6 +1664,42 @@ and the refinement is repeated.
         hist.fit_fixed_points()
         gpx.save()
 
+Specify Instrument Parameters Directly
+-----------------------------------------
+
+Rather than read instrument parameters from a file, it is also possible
+to specify them directly in a script. See the documentation on instrument
+parameter file contents, :ref:`CWPowder_table` and :ref:`TOFPowder_table`
+for more information on the parameters supplied here. 
+
+.. code-block::  python
+
+    import G2script as G2sc
+    import os
+    datadir = os.path.expanduser("~/Scratch/peakfit")
+    PathWrap = lambda fil: os.path.join(datadir,fil)
+    gpx = G2sc.G2Project(newgpx=PathWrap('pkfit.gpx'))
+    # specify instrmental parameters dictionaries
+    inst_params = [
+        {
+            "Type": ["PXC", "PXC", 0],
+            "Lam": [1.5405, 1.5405, 0],
+            "Zero": [0.0, 0.0, 0],
+            "Polariz.": [0.7, 0.7, 0],
+            "U": [2.0, 2.0, 0],
+            "V": [-2.0, -2.0, 0],
+            "W": [5.0, 5.0, 0],
+            "X": [0.0, 0.0, 0],
+            "Y": [0.0, 0.0, 0],
+            "Z": [0.0, 0.0, 0],
+            "SH/L": [0.002, 0.002, 0],
+            "Azimuth": [0.0, 0.0, 0],
+            "Bank": [1, 1, 0],
+        },
+        {},
+    ]
+    hist = gpx.add_powder_histogram(PathWrap('FAP.XRA'), fmthint='GSAS powder',
+                                    iparams=inst_params)
 
 .. _CommandlineInterface: