add download button

app.py

@@ -56,7 +56,7 @@ estimated_expression = estimated_expression["estimated_expression"].to_pandas()
 #DEBUG
 print(f"estimated_expression shape: {estimated_expression.shape}")
 
-col1, col2, padding = st.columns(spec = [0.2, 0.2, 0.6])
+col1, col2, col3, padding = st.columns(spec = [0.2, 0.2, 0.2, 0.4])
 with col1:
     gene_id_1 = st.text_input(
         label = "Gene ID 1",
@@ -94,6 +94,15 @@ chart_data = chart_data.merge(
     right = estimated_expression_meta,
     on = "run_accession")
 
+with col3:
+    st.text('') # help alignment with input box
+    st.download_button(
+        label = "Download data as TSV",
+        data = chart_data.to_csv(sep ='\t').encode('utf-8'),
+        file_name = f"CryptoCEN_expression_{gene_id_1}_vs_{gene_id_2}.tsv",
+        mime = "text/csv")
+
+
 st.markdown(f"""
 #### Gene 1:
 * *Gene ID*: [{gene_id_1}](https://fungidb.org/fungidb/app/record/gene/{gene_id_1})