Zineb Aly
--- a/km3io/aanet.py
+++ b/km3io/aanet.py


-class AanetReader:
+class AanetKeys:
+    "wrapper for aanet keys"
+
+    def __init__(self, file_path):
+        self._file_path = file_path
+        self._events_keys = None
+        self._hits_keys = None
+        self._tracks_keys = None
+        self._mc_hits_keys = None
+        self._mc_tracks_keys = None
+        self._valid_keys = None
+
+    def __repr__(self):
--- a/km3io/aanet.py
+++ b/km3io/aanet.py
+                if key.decode('utf-8') not in fake_branches
+            ] + t_baskets
+        return self._events_keys
+
+    @property
+    def hits_keys(self):
+        if self._hits_keys is None:
+            tree = uproot.open(self._file_path)['E']['hits']
+            self._hits_keys = [key.decode('utf8') for key in tree.keys()]
+        return self._hits_keys
+
+    @property
+    def tracks_keys(self):
+        if self._tracks_keys is None:
+            fake_branches = ['trks.usr_data',
+                             'trks.usr_names']  # uproot can't read these
--- a/km3io/aanet.py
+++ b/km3io/aanet.py
+    @property
+    def valid_keys(self):
+        """constructs a list of all valid keys to be read from an Aanet event file.
+        Returns
+        -------
+        list
+            list of all valid keys.
+    """
+        if self._valid_keys is None:
+            self._valid_keys = (self.events_keys + self.hits_keys +
+                                self.tracks_keys + self.mc_tracks_keys +
+                                self.mc_hits_keys)
+        return self._valid_keys
+
+
+class Reader(AanetKeys):
--- a/km3io/aanet.py
+++ b/km3io/aanet.py
            not contain data. Therefore, the keys corresponding to these fake
            branches are not read.
        """
-        if key not in self.keys() and not isinstance(key, int):
+        if key not in self.valid_keys and not isinstance(key, int):
--- a/km3io/aanet.py
+++ b/km3io/aanet.py
-        return len(self.lazy_data)
+        return self._lazy_data[key]

-    def __repr__(self):
-        return '\n'.join([
-            "Number of events: {}".format(self.__len__()),
-            "Events keys are:\n\t" + '\n\t'.join(self.events_keys),
-            "Hits keys are:\n\t" + '\n\t'.join(self.hits_keys),
-            "Tracks keys are:\n\t" + '\n\t'.join(self.tracks_keys),
-            "Mc hits keys are:\n\t" + '\n\t'.join(self.mc_hits_keys),
-            "Mc tracks keys are:\n\t" + '\n\t'.join(self.mc_tracks_keys)
-        ])

-    def keys(self):
-        """constructs a list of all valid keys to be read from an Aanet event file.
+class AanetReader(AanetKeys):
--- a/km3io/aanet.py
+++ b/km3io/aanet.py
+            "{:15} {:^10} {:>10}".format(k, ':', str(v))
+            for k, v in zip(self._keys, self._values)
+        ])
+
+    def __repr__(self):
+        return str(self)
+
+
+class AanetHits:
+    "wrapper for Aanet hits, manages the display of all hits in one event"
+
+    def __init__(self, keys, values):  # values is a list of lists
+        self._keys = keys  # list of keys
+        self._values = values
+        for k, v in zip(self._keys, self._values):
+            setattr(self, k.split('hits.')[1].replace('.', '_'), v)