diff --git a/xray/storage.py b/storage.py
similarity index 65%
rename from xray/storage.py
rename to storage.py
index 5d41e2f..6185a34 100644
--- a/xray/storage.py
+++ b/storage.py
@@ -1,4 +1,4 @@
-""" npz/hdf5 file based storage; 
+""" npy/npz/hdf5 file based storage; 
     this modules adds the possibility to dump and load objects in files and
     a more convenient was of accessing the data via the .attributedict thanks
     to the DataStorage class """
@@ -11,7 +11,7 @@ import logging
 log = logging.getLogger(__name__)  # __name__ is "foo.bar" here
 
 def unwrapArray(a,recursive=True,readH5pyDataset=True):
-  """ This function takes an object (like a dictionary) and recursivively
+  """ This function takes an object (like a dictionary) and recursively
       unwraps it solving many issues like the fact that many objects are 
       packaged as 0d array
       This funciton has also some specific hack for handling h5py limit to 
@@ -57,6 +57,7 @@ def dictToH5Group(d,group):
 
 def dictToH5(h5,d):
   """ Save a dictionary into an hdf5 file
+      TODO: add capability of saving list of array
       h5py is not capable of handling dictionaries natively"""
   h5 = h5py.File(h5,mode="w")
 #  group = h5.create_group("/")
@@ -74,19 +75,47 @@ def npzToDict(npzFile):
   d = unwrapArray(d,recursive=True)
   return d
 
+def npyToDict(npyFile):
+  d = unwrapArray( np.load(npyFile).item() ,recursive=True)
+  return d
+
 def dictToNpz(npzFile,d): np.savez(npzFile,**d)
+def dictToNpy(npyFile,d): np.save(npyFile,d)
+
+def objToDict(o,recursive=True):
+  """ convert a DictWrap to a dictionary (useful for saving); it should work for other objects too 
+      TODO: this function does not catch a list of DataStorage instances like
+      objToDict( ( DataStorage(), DataStorage() ) )
+      is not converted !!
+  """
+  if "items" not in dir(o): return o 
+  d = dict()
+  for k,v in o.items():
+    try:
+      d[k] = objToDict( v )
+    except Exception as e:
+      log.info("In objToDict, could not convert key %s to dict, error was"%\
+                (k,e))
+      d[k] = v
+  return d
+
 
 def read(fname):
   extension = os.path.splitext(fname)[1]
   log.info("Reading storage file %s"%fname)
   if extension == ".npz": 
     return DataStorage(npzToDict(fname))
+  elif extension == ".npy": 
+    return DataStorage(npyToDict(fname))
   elif extension == ".h5":
     return DataStorage(h5ToDict(fname))
   else:
-    raise ValueError("Extension must be h5 or npz, it was %s"%extension) 
+    raise ValueError("Extension must be h5, npy or npz, it was %s"%extension) 
 
 def save(fname,d):
+  # make sure the object is dict (recursively) this allows reading it
+  # without the DataStorage module
+  d = objToDict(d,recursive=True)
   extension = os.path.splitext(fname)[1]
   log.info("Saving storage file %s"%fname)
   try:
@@ -94,24 +123,57 @@ def save(fname,d):
       return dictToNpz(fname,d)
     elif extension == ".h5":
       return dictToH5(fname,d)
+    elif extension == ".npy":
+      return dictToNpy(fname,d)
     else:
-      raise ValueError("Extension must be h5 or npz") 
+      raise ValueError("Extension must be h5, npy or npz, it was %s"%extension) 
   except Exception as e:
     log.exception("Could not save %s"%fname)
 
+
 class DataStorage(dict):
-  """ Storage for 1d integrated info """
-  def __init__(self,fileOrDict,recursive=True,
-               default_name='pyfai_1d',default_ext='npz'):
-    if isinstance(fileOrDict,dict):
-      self.filename = None
-      d = fileOrDict
+  """ Storage for dict like object.
+      recursive : bool
+         recursively convert dict-like objects to DataStorage
+      It can save data to file (format npy,npz or h5)
+
+      To initialize it:
+
+        data = DataStorage( dict( a=(1,2,3),b="add"),filename='store.npz' )
+
+        data = DataStorage( a=(1,2,3), b="add" )
+
+        reads from file if it exists
+        data = DataStorage( 'mysaveddata.npz' ) ;
+
+        DOES NOT READ FROM FILE (even if it exists)!!
+        data = DataStorage( filename = 'mysaveddata.npz' ); 
+
+        create empty storage (with default filename)
+        data = DataStorage()
+  """
+  def __init__(self,*args,filename='data_storage.npz',recursive=True,**kwargs):
+#    self.filename = kwargs.pop('filename',"data_storage.npz")
+    self.filename = filename
+    # interpret kwargs as dict if there are
+    if len(kwargs) != 0:
+      fileOrDict = dict(kwargs)
+    elif len(kwargs)==0 and len(args)>0:
+      fileOrDict = args[0]
     else:
-      assert isinstance(fileOrDict,str)
-      if os.path.isdir(fileOrDict):
-        fileOrDict = fileOrDict + "/" + default_name + "." + default_ext
-      self.filename = fileOrDict
-      d = read(fileOrDict)
+      fileOrDict = dict()
+
+    d = dict(); # data dictionary
+    if isinstance(fileOrDict,dict):
+      d = fileOrDict
+    elif isinstance(fileOrDict,str):
+      if os.path.exists(fileOrDict):
+        d = read(fileOrDict)
+      else:
+        self.filename=fileOrDict
+        d = dict()
+    else:
+      raise ValueError("Invalid DataStorage definition")
 
     if recursive:
       for k in d.keys():
@@ -150,7 +212,7 @@ class DataStorage(dict):
     s = ["DataStorage obj containing (sorted): ",]
     for k in keys:
       if isinstance(self[k],np.ndarray):
-        value_str = "array %s"% "x".join(map(str,self[k].shape))
+        value_str = "array, size %s, type %s"% ("x".join(map(str,self[k].shape)),self[k].dtype)
       elif isinstance(self[k],DataStorage):
         value_str = str(self[k])[:50] + "..."
       elif isinstance(self[k],(str,DataStorage)):
@@ -165,4 +227,4 @@ class DataStorage(dict):
   def save(self,fname=None):
     if fname is None: fname = self.filename
     assert fname is not None
-    save(fname,dict(self))
+    save(fname,self)