rheed_data/layer_N has now attr NXclass set to "NXsubentry"

now many of the instructions prev. under the __name__ = "__main__"
condition have their own function (now called main())

src/main.py

@@ -771,6 +771,7 @@ def build_nexus_file(pld_fabrication, output_path="output/nffa-di_unnamed.h5"):
         rheed_data = pld_fabrication["rheed_data"]
         for layer in rheed_data:
             nx_rheed_layer = nx_rheed.create_group(layer)
+            nx_rheed_layer.attrs["NX_class"] = "NXsubentry"
 
             layer_dict = rheed_data[layer]
             n = layer_dict["layer_number"]
@@ -873,6 +874,39 @@ def build_nexus_file(pld_fabrication, output_path="output/nffa-di_unnamed.h5"):
     #   * Layer.fetch_images() - dictionary
 
 
+def main(
+    api_key,
+    ELABFTW_API_URL,
+    elabid,
+):
+    handler = APIHandler(api_key, ELABFTW_API_URL)
+    sample_raw_data = handler.get_entry_from_elabid(elabid)
+    sample = Entrypoint(sample_raw_data)
+    sample_name = sample.name.strip().replace(
+        " ", "-"
+    )  # returns error if no "title" or title is not str
+    # Less important variables:
+    operative_unit = os.getenv("operative_unit") or None
+    if operative_unit:
+        operative_unit = operative_unit.strip().replace(" ", "-")
+    if sample.proposal:
+        sample_proposal = call_proposal_from_elabid(sample.proposal)
+    else:
+        sample_proposal = None
+    substrate_object = chain_entrypoint_to_batch(sample)  # Substrate-class object
+    layers = chain_entrypoint_to_layers(sample)  # list of Layer-class objects
+    # n_layers = len(layers)  # total number of layers on the sample
+    fn_base = (
+        "nffa-di_"
+        + (f"{sample_proposal}_" if sample_proposal else "")
+        + (f"{operative_unit}_" if operative_unit else "")
+        + "PLD_"
+        + sample_name[:9]
+    )
+    result = make_nexus_schema_dictionary(substrate_object, layers)
+    return {"result": result, "fn_base": fn_base}
+
+
 if __name__ == "__main__":
     load_dotenv()
     api_key = os.getenv("api_key") or getpass("Paste API key here: ", echo_char="*")
@@ -884,32 +918,16 @@ if __name__ == "__main__":
     ELABFTW_API_URL = os.getenv("ELABFTW_API_URL") or input(
         "Enter a valid eLabFTW API URL (ends with '/api/v2)': "
     )
-    handler = APIHandler(api_key, ELABFTW_API_URL)
+
-    data = handler.get_entry_from_elabid(elabid)
+    output = main(
-    sample = Entrypoint(data)
+        api_key,
-    sample_name = sample.name.strip().replace(
+        ELABFTW_API_URL,
-        " ", "-"
+        elabid,
-    )  # returns error if no "title" or title is not str
-    operative_unit = os.getenv("operative_unit") or None
-    if operative_unit:
-        operative_unit = operative_unit.strip().replace(" ", "-")
-    if sample.proposal:
-        sample_proposal = call_proposal_from_elabid(sample.proposal)
-    else:
-        sample_proposal = None
-    substrate_object = chain_entrypoint_to_batch(sample)  # Substrate-class object
-    layers = chain_entrypoint_to_layers(sample)  # list of Layer-class objects
-    n_layers = len(layers)  # total number of layers on the sample
-    # print(make_nexus_schema_dictionary(substrate_object, layers)) # debug
-    fn_base = (
-        "nffa-di_"
-        + (f"{sample_proposal}_" if sample_proposal else "")
-        + (f"{operative_unit}_" if operative_unit else "")
-        + "PLD_"
-        + sample_name[:9]
     )
 
-    result = make_nexus_schema_dictionary(substrate_object, layers)
+    result = output["result"]
+    fn_base = output["fn_base"]
+
     with open(f"output/{fn_base}.json", "w") as f:
         json.dump(result, f, indent=3)