diff --git a/Common/util_eddies.py b/Common/util_eddies.py
index a663117d76a68d914a1be4123928f5d2e035416e..abf988814e0d565a1989568f33eb03c0bb64c2e9 100644
--- a/Common/util_eddies.py
+++ b/Common/util_eddies.py
@@ -7,6 +7,11 @@ import bisect
 import os
 
 class SHPC_class:
+    """We are assuming that eddies are indexed from 1, without jump, for
+    each date.
+
+    """
+
     def __init__(self, SHPC_dir, def_orient):
         """def_orient, for default orientation, is used to define d_init and
         n_dates. Since we are going to open files, we might as