Source Code for Module qm.db

  1  ######################################################################## 
  2  # 
  3  # File:   db.py 
  4  # Author: Nathaniel Smith <njs@codesourcery.com 
  5  # Date:   2003-06-13 
  6  # 
  7  # Contents: 
  8  #   A few simple functions to help with connecting to SQL databases 
  9  #   and using the DB 2.0 API. 
 10  # 
 11  # Copyright (c) 2003 by CodeSourcery, LLC.  All rights reserved.  
 12  # 
 13  # For license terms see the file COPYING. 
 14  # 
 15  ######################################################################## 
 16   
 17  ######################################################################## 
 18  # Imports 
 19  ######################################################################## 
 20   
 21  import os 
 22   
 23  ######################################################################## 
 24  # Classes 
 25  ######################################################################## 
 26   
 27 -class Connection: 
 28      """A wrapper around a DB 2.0 connection. 
 29   
 30      Provides a minimal but consistent interface to an underlying 
 31      database connection.  In particular, a 'Connection' quotes SQL 
 32      queries as necessary for the underlying DB 2.0 connection.""" 
 33   
 34 -    def __init__(self, module_name, *args, **more_args): 
 35          """Uses the given DB 2.0 module to connect to a database. 
 36   
 37          'module_name' -- The DB 2.0-compliant module to use to connect, 
 38          for example "pgdb". 
 39   
 40          'args' -- Positional arguments to pass to the module's 'connect' 
 41          method. 
 42   
 43          'more_args' -- Keyword arguments to pass to the module's 
 44          'connect' method.""" 
 45   
 46          # Last argument  must be a non-empty list or __import__ will 
 47          # return the wrong module. 
 48          self._module = __import__(module_name, 
 49                                    globals(), 
 50                                    locals(), 
 51                                    [""]) 
 52          self._connection = self._module.connect(*args, **more_args) 
 53   
 54   
 55 -    def close(self): 
 56   
 57          self._connection.close() 
 58   
 59   
 60 -    def commit(self): 
 61   
 62          self._connection.commit() 
 63   
 64   
 65 -    def rollback(self): 
 66   
 67          self._connection.rollback() 
 68   
 69   
 70 -    def execute(self, sql): 
 71          """Execute a SQL statement in this database. 
 72   
 73          If this database requires any overall quoting of the given SQL 
 74          (for instance, doubling of %'s), it will be performed by this 
 75          method. 
 76   
 77          returns -- A database cursor. 
 78           
 79          """ 
 80   
 81          # According to the DB 2.0 spec, the following lines should be 
 82          # necessary.  But in fact it seems that the database modules we 
 83          # use do not strip doubled %'s inside SQL string constants, and 
 84          # do not try to expand parameters inside SQL string constants. 
 85          # Since string constants are the main place where %'s may occur, 
 86          # we do not quote %'s at all. 
 87          #if self._module.paramstyle in ["format", "pyformat"]: 
 88          #    sql = sql.replace("%", "%%") 
 89          cursor = self._connection.cursor() 
 90           
 91          cursor.execute(sql) 
 92          return cursor 
 93           
 94   
 95  ######################################################################## 
 96  # Functions 
 97  ######################################################################## 
 98   
 99 -def quote_string(string): 
100      """Quotes a string for SQL. 
101   
102      'string' -- A string whose contents are to be used in an SQL literal 
103      string. 
104   
105      returns -- A SQL literal string whose contents match that of 
106      'string'.""" 
107   
108      # Replace each ' with '', then surround with more 's.  Also double 
109      # backslashes.  It'd be nice to handle things like quoting non-ASCII 
110      # characters (by replacing them with octal escapes), but we don't. 
111      return "'" + string.replace("'", "''").replace("\\", "\\\\") + "'" 
112   
113  ######################################################################## 
114  # Local Variables: 
115  # mode: python 
116  # indent-tabs-mode: nil 
117  # fill-column: 72 
118  # End: 
119