Python ODBC Wrapper

ODBC with Python

• http://www.petersblog.org/node/847

   1  #
   2  # Database wrapper class.
   3  #
   4  import odbc
   5  import os
   6  import traceback
   7  
   8  class DBTable:
   9      """
  10      Wrapper for database table
  11      """
  12      FIELD_TYPE = 0
  13  
  14      def __init__( self, oConnection, strTable):
  15          self.oConnection = oConnection
  16          self.strTable = strTable
  17  
  18          oCursor = oConnection.cursor()
  19          oCursor.execute( "SELECT * FROM %s" % strTable)
  20  
  21          self.oFields = [ oField[0] for oField in oCursor.description]
  22          self.oFieldDescription = dict( [ (oField[0],
  23                                        oField[1:]) for oField in oCursor.description])
  24  
  25      def Select( self, strQuery):
  26          """
  27          Select records from query
  28  
  29          Takes either SQL of select statement or a dictionary containing
  30          field names and values to find.
  31          """
  32          self.oCursor = self.oConnection.cursor()
  33          if type( strQuery) == type(""):
  34              self.oCursor.execute( strQuery)
  35          else:
  36              #
  37              # assume query is a dict
  38              #
  39              self.oCursor.execute( "SELECT * FROM %s WHERE %s" % (self.strTable,
  40                                                          self.DictToWhere( strQuery)))
  41  
  42      def FetchOne( self):
  43          """
  44          Get next row of results
  45          Returns a dictionary holding field names and values.
  46          """
  47          oRow = self.oCursor.fetchone()
  48          if oRow:
  49              """
  50              Build a dictionary to map field name->value
  51              """
  52              return dict([(self.oFields[i], oRow[i]) for i in range(len(oRow))])
  53          else:
  54              return None
  55  
  56      def Insert( self, oDict):
  57          """
  58          Insert a row in the database
  59          Takes a dictionary holding field names and values.
  60          """
  61          strFields = oDict.keys()
  62          strValues = []
  63          for strField in strFields:
  64              strValue = oDict[strField]
  65              strType = self.oFieldDescription[strField][DBTable.FIELD_TYPE]
  66  
  67              strValues.append( self.FormatField( strField, strValue))
  68  
  69          strSQL = "INSERT INTO %s ( %s) VALUES(%s);" % ( self.strTable,
  70                                                           ", ".join( strFields),
  71                                                           ", ".join( strValues))
  72          print strSQL
  73          oCursor = self.oConnection.cursor()
  74          oCursor.execute( strSQL)
  75          self.oConnection.commit()
  76  
  77      def Delete( self, oDict):
  78          """
  79          Delete row based on dictionary contents
  80          Takes a dictionary holding field names and values.
  81          """
  82          strSQL = "DELETE FROM %s WHERE %s;" % ( self.strTable, self.DictToWhere( oDict))
  83          print strSQL
  84          oCursor = self.oConnection.cursor()
  85          oCursor.execute( strSQL)
  86          self.oConnection.commit()
  87  
  88      def DictToWhere( self, oDict):
  89          """
  90          Convert dictionary to WHERE clause.
  91          """
  92          strFields = oDict.keys()
  93          strExpressions = []
  94  
  95          for strField in strFields:
  96              strValue = oDict[strField]
  97              strType = self.oFieldDescription[strField][DBTable.FIELD_TYPE]
  98  
  99              strValue = self.FormatField( strField, strValue)
 100  
 101              strExpressions.append( '%s = %s' % (strField, strValue))
 102  
 103          return " AND ".join( strExpressions)
 104  
 105      def FormatField( self, strField, strValue):
 106          """
 107          Format a field for an sql statement.
 108          """
 109          strType = self.oFieldDescription[strField][DBTable.FIELD_TYPE]
 110          if strType == 'STRING':
 111              return "'%s'" % str(strValue).replace( "'", "''")
 112          elif strType == 'NUMBER':
 113              return '%d' % int( strValue)
 114          else:
 115              raise 'unknown field type %s' % strType
 116