You can now import and export IFCCSV to the current file in memory without writing to disk

src/ifccsv/ifccsv.py

@@ -131,8 +131,7 @@ class IfcCsv:
                 results.update([p.Name for p in element.Quantities])
         return ["{}.{}".format(pset_qto_name, n) for n in results]
 
-    def Import(self, ifc):
-        ifc_file = ifcopenshell.open(ifc)
+    def Import(self, ifc_file):
         with open(self.output, newline="", encoding="utf-8") as f:
             reader = csv.reader(f, delimiter=self.delimiter)
             headers = []
@@ -149,7 +148,6 @@ class IfcCsv:
                     if i == 0:
                         continue  # Skip GlobalId
                     element = IfcAttributeSetter.set_element_key(ifc_file, element, headers[i], value)
-        ifc_file.write(ifc)
 
 
 if __name__ == "__main__":
@@ -174,4 +172,6 @@ if __name__ == "__main__":
     elif getattr(args, "import"):
         ifc_csv = IfcCsv()
         ifc_csv.output = args.csv
-        ifc_csv.Import(args.ifc)
+        ifc_file = ifcopenshell.open(args.ifc)
+        ifc_csv.Import(ifc_file)
+        ifc_file.write(args.ifc)