fixed DynamicOneDimensionalArray's size

Author: Naveen-Pal

pydatastructs/linear_data_structures/arrays.py

@@ -421,6 +421,9 @@ def delete(self, idx):
     @property
     def size(self):
         return self._size
+    
+    def __len__(self):
+        return self._num
 
     def __str__(self):
         to_be_printed = ['' for _ in range(self._last_pos_filled + 1)]