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#!/usr/bin/python
"""
Module Name: gadflyBrowse
Description: Plug in for PythonCard application dbBrowse to provide Gadfly specific functionality
Constant/configuration values are currently maintained in the source code. If we are to optimise this application they should be split into seperate configuration files (as per PythonCard/Webware style guidelines)
The structure of this module should be replicated for different RDBMS so that they can be interchanged by dbBrowse - hopefully.
"""
__version__="$Revision $"[11:-2]
__date__="$Date $"
__author__="Andy Todd <andy47@halfcooked.com>"
import gadfly
class browse:
# Connection should be a dictionary with at least two keys,
# 'databasename' and 'directory'
# This is wildly different to other database modules
def __init__(self, connection):
"Setup the database connection"
self._system_tables=['__TABLE_NAMES__', '__INDEXCOLS__', '__COLUMNS__', '__INDICES__', '__DATADEFS__', 'DUAL']
# Not providing a db name is guaranteed to ruin our connection
if not connection['databasename']:
raise ValueError
self._db = gadfly.gadfly( databasename=connection['databasename']
,directory=connection['directory'] )
self._cursor=self._db.cursor()
# This one is used in getRow
self._tableName=''
def getTables(self):
"Return a list of all of the non-system tables in <database>"
stmt = "SELECT table_name FROM __table_names__"
self._cursor.execute(stmt)
# I'm using a list comprehension here instead of a for loop,
# either will do but I think this is more concise (unlike this comment)
return [ x[0] for x in self._cursor.fetchall() if x[0] not in self._system_tables ]
def getColumns(self, tableName):
"Get the definition of the columns in tableName"
stmt = "SELECT column_name FROM __columns__ WHERE table_name = ?"
self._cursor.execute(stmt, (tableName,))
# format of Gadfly definitions is;
# column name
# format of dbBrowser column definitions is
# column name, data type, length (for display), nullable, key, default
columnDefs = []
for column in self._cursor.fetchall():
columnName = column[0]
dataType, nullable, key, default = "varchar", "", "", ""
# Dodgy default, but if works for me
precision = 255
columnDefs.append((columnName, dataType, precision, nullable, key, default))
return columnDefs
def getQueryString(self, tableName):
"Return a SQL statement which queries all of the columns in tableName"
tableStructure=self.getColumns(tableName)
# Construct and return the string
stmt='SELECT '
for columnList in tableStructure:
stmt+=columnList[0]+', '
stmt=stmt[:-2]+' FROM '+tableName
return stmt
def getRow(self, tableName):
"Get a row from tableName"
# When we upgrade to 2.2 this will be a great candidate for a
# generator/iterator. In the meantime we use self._tableName to keep
# track of what we are doing
if tableName!=self._tableName:
self._tableName=tableName
self._cursor.execute(self.getQueryString(tableName))
try:
result = self._cursor.fetchone()
except gadfly.database.error:
result = None
return result
def getRows(self, tableName):
"Get all of the rows from tableName"
if tableName!=self._tableName:
self._tableName=tableName
self._cursor.execute(self.getQueryString(tableName))
try:
result = self._cursor.fetchall()
except gadfly.database.error:
result = None
return result
if __name__ == '__main__':
# We are in an interactive session so run our test routines
# Connect to the database
connection={ 'databasename':'andy'
,'directory':'E:\Gadfly'}
dbHolder = browse(connection)
# Return all of our table names into user_tables
user_tables = dbHolder.getTables()
# Print out the structure of each table and its first row
print "--------------------------------------------------"
for table in user_tables:
print dbHolder.getQueryString(table)
print dbHolder.getRow(table)
print "--------------------------------------------------"
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