diff --git a/jupyter-openbis-extension/dataset.py b/jupyter-openbis-extension/dataset.py
index 9a656c74d94a806a82ff8216b7dd1937f4a56d42..91c6a89488dead78c42bef4fba4292b6122bfdf3 100644
--- a/jupyter-openbis-extension/dataset.py
+++ b/jupyter-openbis-extension/dataset.py
@@ -127,12 +127,13 @@ class DataSetUploadHandler(IPythonHandler):
                 return
 
         errors = []
-        print("--------------_HERE_-----------1")
 
         sample = None
         experiment = None
 
         if (data.get('entityIdentifier')):
+            sample = None
+            experiment = None
             try:
                 sample = conn.openbis.get_sample(data.get('entityIdentifier'))
             except Exception as e:
@@ -152,8 +153,6 @@ class DataSetUploadHandler(IPythonHandler):
                 {"entityIdentifier": "please provide a sample or experiment identifier"}
             )
 
-        print("--------------_HERE_-----------2")
-
         parents = []
         if data.get('parents'):
             parents = data.get('parents')
@@ -165,8 +164,6 @@ class DataSetUploadHandler(IPythonHandler):
                         "parent": "Parent DataSet not found: {}".format(parent)
                     })
 
-        print("--------------_HERE_-----------2a")
-
         filenames = []
         for filename in data.get('files'):
             filename = unquote(filename)
@@ -176,7 +173,6 @@ class DataSetUploadHandler(IPythonHandler):
                 errors.append({
                     "file": "File not found: {}".format(filename)
                 })
-        print("--------------_HERE_-----------3")
 
         try:
             dataset = conn.openbis.new_dataset(
@@ -191,7 +187,6 @@ class DataSetUploadHandler(IPythonHandler):
             errors.append({
                 "create": 'Error while creating the dataset: {}'.format(e)
             })
-        print("--------------_HERE_-----------4")
 
         # try to set the properties
         if data.get('props'):
@@ -211,14 +206,12 @@ class DataSetUploadHandler(IPythonHandler):
                     errors.append({
                         "prop."+prop_name : "is mandatory"
                     })
-        print("--------------_HERE_-----------5")
 
         # write errors back if already occured
         if errors:
             self.set_status(500)
             self.write({ "errors": errors })
             return
-        print("--------------_HERE_-----------6")
 
         try:
             dataset.save()
@@ -226,7 +219,6 @@ class DataSetUploadHandler(IPythonHandler):
             errors.append({
                 "save": 'Error while saving the dataset: {}'.format(e)
             })
-        print("--------------_HERE_-----------7")
 
         # write errors back if they occured
         if errors:
@@ -238,9 +230,7 @@ class DataSetUploadHandler(IPythonHandler):
                 'status': 200,
                 'statusText': 'Jupyter Notebook was successfully uploaded to: {} with permId: {}'.format(conn.name, dataset.permId)
             })
-
         print('Jupyter Notebook was successfully uploaded to: {} with permId: {}'.format(conn.name, dataset.permId))
-        print("--------------_HERE_-----------8")
 
     def post(self, **params):
         """Handle a request to /openbis/dataset/connection_name/permId
@@ -256,8 +246,6 @@ class DataSetUploadHandler(IPythonHandler):
             return
 
         data = self.get_json_body()
-        print("Received DATA")
-        print(data)
         self.upload_data(conn=conn,data=data)
 
 
diff --git a/jupyter-openbis-extension/sample.py b/jupyter-openbis-extension/sample.py
index 752dfe710c37eb4cf0af6fdf48d8b3fd63310f8a..83f4a30ad09c75e5531a0e08325cbb397c27a647 100644
--- a/jupyter-openbis-extension/sample.py
+++ b/jupyter-openbis-extension/sample.py
@@ -7,6 +7,8 @@ from urllib.parse import parse_qs
 
 
 def get_entity_for_identifier(conn, identifier):
+
+    entity = None
     try:
         entity = conn.openbis.get_sample(identifier)
     except Exception as exc:
@@ -17,9 +19,9 @@ def get_entity_for_identifier(conn, identifier):
             entity = conn.openbis.get_experiment(identifier)
         except Exception as exc:
             pass
-
     return entity
 
+
 def get_datasets(entity, start_with=None, count=None):
 
     datasets = entity.get_datasets(start_with=start_with, count=count)