Update app.py

app.py

@@ -40,6 +40,8 @@ class PaperDownloader:
 
     def clean_doi(self, doi):
         """Clean and encode DOI for URL"""
+        if not isinstance(doi, str):
+           return None
         return quote(doi.strip()) if doi else None
 
     def download_paper_scihub(self, doi):
@@ -219,7 +221,9 @@ class PaperDownloader:
             pdf_content = self.download_with_retry(doi)
             
             if pdf_content:
-                filename = f"{doi.replace('/', '_').replace('.', '_')}.pdf"
+                if doi is None:
+                     return None, "Error: DOI not provided", "Error: DOI not provided"
+                filename = f"{str(doi).replace('/', '_').replace('.', '_')}.pdf"
                 filepath = os.path.join(self.output_dir, filename)
                 with open(filepath, 'wb') as f:
                     f.write(pdf_content)
@@ -295,7 +299,9 @@ class PaperDownloader:
                 
                 # Save PDF
                 if pdf_content:
-                    filename = f"{doi.replace('/', '_').replace('.', '_')}.pdf"
+                    if doi is None:
+                        return None, "Error: DOI not provided", "Error: DOI not provided", None
+                    filename = f"{str(doi).replace('/', '_').replace('.', '_')}.pdf"
                     filepath = os.path.join(self.output_dir, filename)
                     
                     with open(filepath, 'wb') as f:
@@ -319,7 +325,7 @@ class PaperDownloader:
                     zipf.write(file_path, arcname=os.path.basename(file_path))
             logger.info(f"ZIP file created: {zip_filename}")
 
-        return zip_filename, "\n".join(downloaded_files), "\n".join(failed_dois)
+        return zip_filename, "\n".join(downloaded_files), "\n".join(failed_dois), None
 
 
 def create_gradio_interface():
@@ -379,7 +385,8 @@ def create_gradio_interface():
             border-radius: 10px;
             box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
         }
-        """
+        """,
+        cache_examples=False
     )
 
     return interface