Correct comment

IPython/html/services/sessions/sessionmanager.py

@@ -1,222 +1,222 b''
 """A base class session manager.
 
 Authors:
 
 * Zach Sailer
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2013  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import uuid
 import sqlite3
 
 from tornado import web
 
 from IPython.config.configurable import LoggingConfigurable
 from IPython.utils.py3compat import unicode_type
 from IPython.utils.traitlets import Instance
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
 class SessionManager(LoggingConfigurable):
 
     kernel_manager = Instance('IPython.html.services.kernels.kernelmanager.MappingKernelManager')
     contents_manager = Instance('IPython.html.services.contents.manager.ContentsManager', args=())
     
     # Session database initialized below
     _cursor = None
     _connection = None
     _columns = {'session_id', 'name', 'path', 'kernel_id'}
     
     @property
     def cursor(self):
         """Start a cursor and create a database called 'session'"""
         if self._cursor is None:
             self._cursor = self.connection.cursor()
             self._cursor.execute("""CREATE TABLE session 
                 (session_id, name, path, kernel_id)""")
         return self._cursor
 
     @property
     def connection(self):
         """Start a database connection"""
         if self._connection is None:
             self._connection = sqlite3.connect(':memory:')
             self._connection.row_factory = sqlite3.Row
         return self._connection
         
     def __del__(self):
         """Close connection once SessionManager closes"""
         self.cursor.close()
 
     def session_exists(self, name, path):
         """Check to see if the session for a given notebook exists"""
         self.cursor.execute("SELECT * FROM session WHERE name=? AND path=?", (name, path))
         reply = self.cursor.fetchone()
         if reply is None:
             return False
         else:
             return True
 
     def new_session_id(self):
         "Create a uuid for a new session"
         return unicode_type(uuid.uuid4())
 
     def create_session(self, name=None, path=None, kernel_name='python'):
         """Creates a session and returns its model"""
         session_id = self.new_session_id()
         # allow nbm to specify kernels cwd
         kernel_path = self.contents_manager.get_kernel_path(name=name, path=path)
         kernel_id = self.kernel_manager.start_kernel(path=kernel_path,
                                                      kernel_name=kernel_name)
         return self.save_session(session_id, name=name, path=path,
                                  kernel_id=kernel_id)
 
     def save_session(self, session_id, name=None, path=None, kernel_id=None):
         """Saves the items for the session with the given session_id
         
         Given a session_id (and any other of the arguments), this method
         creates a row in the sqlite session database that holds the information
         for a session.
         
         Parameters
         ----------
         session_id : str
             uuid for the session; this method must be given a session_id
         name : str
             the .ipynb notebook name that started the session
         path : str
             the path to the named notebook
         kernel_id : str
             a uuid for the kernel associated with this session
         
         Returns
         -------
         model : dict
             a dictionary of the session model
         """
         self.cursor.execute("INSERT INTO session VALUES (?,?,?,?)",
             (session_id, name, path, kernel_id)
         )
         return self.get_session(session_id=session_id)
 
     def get_session(self, **kwargs):
         """Returns the model for a particular session.
         
         Takes a keyword argument and searches for the value in the session
         database, then returns the rest of the session's info.
 
         Parameters
         ----------
         **kwargs : keyword argument
             must be given one of the keywords and values from the session database
             (i.e. session_id, name, path, kernel_id)
 
         Returns
         -------
         model : dict
             returns a dictionary that includes all the information from the 
             session described by the kwarg.
         """
         if not kwargs:
             raise TypeError("must specify a column to query")
 
         conditions = []
         for column in kwargs.keys():
             if column not in self._columns:
                 raise TypeError("No such column: %r", column)
             conditions.append("%s=?" % column)
 
         query = "SELECT * FROM session WHERE %s" % (' AND '.join(conditions))
 
         self.cursor.execute(query, list(kwargs.values()))
         try:
             row = self.cursor.fetchone()
         except KeyError:
             # The kernel is missing, so the session just got deleted.
             row = None
 
         if row is None:
             q = []
             for key, value in kwargs.items():
                 q.append("%s=%r" % (key, value))
 
             raise web.HTTPError(404, u'Session not found: %s' % (', '.join(q)))
 
         return self.row_to_model(row)
 
     def update_session(self, session_id, **kwargs):
         """Updates the values in the session database.
         
         Changes the values of the session with the given session_id
         with the values from the keyword arguments. 
         
         Parameters
         ----------
         session_id : str
             a uuid that identifies a session in the sqlite3 database
         **kwargs : str
             the key must correspond to a column title in session database,
             and the value replaces the current value in the session 
             with session_id.
         """
         self.get_session(session_id=session_id)
 
         if not kwargs:
             # no changes
             return
 
         sets = []
         for column in kwargs.keys():
             if column not in self._columns:
                 raise TypeError("No such column: %r" % column)
             sets.append("%s=?" % column)
         query = "UPDATE session SET %s WHERE session_id=?" % (', '.join(sets))
         self.cursor.execute(query, list(kwargs.values()) + [session_id])
 
     def row_to_model(self, row):
         """Takes sqlite database session row and turns it into a dictionary"""
         if row['kernel_id'] not in self.kernel_manager:
-            # The kernel was killed without deleting the session. Should never occur.
+            # The kernel was killed or died without deleting the session.
             self.delete_session(row['session_id'])
             raise KeyError
 
         model = {
             'id': row['session_id'],
             'notebook': {
                 'name': row['name'],
                 'path': row['path']
             },
             'kernel': self.kernel_manager.kernel_model(row['kernel_id'])
         }
         return model
 
     def list_sessions(self):
         """Returns a list of dictionaries containing all the information from
         the session database"""
         c = self.cursor.execute("SELECT * FROM session")
         result = []
         for row in c:
             try:
                 result.append(self.row_to_model(row))
             except KeyError:
                 pass
         return result
 
     def delete_session(self, session_id):
         """Deletes the row in the session database with given session_id"""
         # Check that session exists before deleting
         session = self.get_session(session_id=session_id)
         self.kernel_manager.shutdown_kernel(session['kernel']['id'])
         self.cursor.execute("DELETE FROM session WHERE session_id=?", (session_id,))