generate hashtable dataframe

alignmentfreegraph.py

@@ -36,6 +36,7 @@ def __init__(self, location: str = None, db_name: str = None, username: str = No
             raise ValueError("k must be greater than 1")
         self.k = k
         self.compute_hashtable()
+        self.hashtable_df = None
 
     def connect(self, location: str = None, db_name: str = None,
                 username: str = None, password: str = None, configuration: [dict, str] = None):  # type: ignore
@@ -341,13 +342,27 @@ def remove_duplicates(self):
             self.hashtable[el[0]].pop(el[1])
 
     def hashtable_to_df(self):
+        """
+        This method generate the hash-table of the graph as a pandas DataFrame
+        """
+        import pandas as pd
+
+        rows = []
+        for key, value in self.hashtable.items():
+            for kmer, colors in value.items():
+                rows.append({'start': key, 'Kmer': kmer, 'colors': colors})
+
+        self.hashtable_df = pd.DataFrame(rows)
+
+    def get_hashtable_df(self):
         """
         This method return the hash-table of the graph as a pandas DataFrame
 
         :return: The hash-table of the graph as a pandas DataFrame
         """
-        import pandas as pd
-        return pd.DataFrame(self.hashtable)
+        if self.hashtable_df is None:
+            self.hashtable_to_df()
+        return self.hashtable_df
 
     def export_hashtable(self, file_path: str):
         """
@@ -357,10 +372,10 @@ def export_hashtable(self, file_path: str):
         """
 
         if file_path.endswith('.csv'):
-            self.hashtable_to_df().to_csv(file_path)
+            self.get_hashtable_df().to_csv(file_path)
 
         elif file_path.endswith('.xlsx'):
-            self.hashtable_to_df().to_excel(file_path)
+            self.get_hashtable_df().to_excel(file_path)
 
         else:
             import json