diff --git a/python/obitools3/utils.pxd b/python/obitools3/utils.pxd
index 0eafa4d..2a1b144 100644
--- a/python/obitools3/utils.pxd
+++ b/python/obitools3/utils.pxd
@@ -1,5 +1,6 @@
 #cython: language_level=3
 
+
 cdef bytes str2bytes(str string)
 
 cdef str bytes2str(bytes string)
\ No newline at end of file
diff --git a/python/obitools3/utils.pyx b/python/obitools3/utils.pyx
index 183b373..793e7f1 100644
--- a/python/obitools3/utils.pyx
+++ b/python/obitools3/utils.pyx
@@ -1,7 +1,28 @@
 #cython: language_level=3
 
+import sys
+import io
+
 cdef bytes str2bytes(str string):
+    """
+    Short cut to convert ascii encoded python string (str) to bytes 
+    which can be easily converted to C-strings. 
+    
+        @param string: the python string to be converted.
+        @type string: str
+        @return a transcoded string
+        @rtype: bytes 
+    """
     return string.encode('ascii')
 
 cdef str bytes2str(bytes string):
-    return string.decode('ascii')
\ No newline at end of file
+    """
+    Short cut to convert bytes (C-strings) to ascii encoded python string (str).
+    
+        @param string: the binary (C-string) string to be converted.
+        @type string: bytes
+        @return an ascii transcoded string
+        @rtype: str 
+    """
+    return string.decode('ascii')
+