Trappings MySQL Warnings on Calls Wrapped in Classes -- Python
- by chernevik
I can't get Python's try/else blocks to catch MySQL warnings when the execution statements are wrapped in classes.
I have a class that has as a MySQL connection object as an attribute, a MySQL cursor object as another, and a method that run queries through that cursor object. The cursor is itself wrapped in a class. These seem to run queries properly, but the MySQL warnings they generate are not caught as exceptions in a try/else block. Why don't the try/else blocks catch the warnings? How would I revise the classes or method calls to catch the warnings?
Also, I've looked through the prominent sources and can't find a discussion that helps me understand this. I'd appreciate any reference that explains this.
Please see code below. Apologies for verbosity, I'm newbie.
#!/usr/bin/python
import MySQLdb
import sys
import copy
sys.path.append('../../config')
import credentials as c # local module with dbase connection credentials
#=============================================================================
# CLASSES
#------------------------------------------------------------------------
class dbMySQL_Connection:
def __init__(self, db_server, db_user, db_passwd):
self.conn = MySQLdb.connect(db_server, db_user, db_passwd)
def getCursor(self, dict_flag=True):
self.dbMySQL_Cursor = dbMySQL_Cursor(self.conn, dict_flag)
return self.dbMySQL_Cursor
def runQuery(self, qryStr, dict_flag=True):
qry_res = runQueryNoCursor(qryStr=qryStr, \
conn=self, \
dict_flag=dict_flag)
return qry_res
#------------------------------------------------------------------------
class dbMySQL_Cursor:
def __init__(self, conn, dict_flag=True):
if dict_flag:
dbMySQL_Cursor = conn.cursor(MySQLdb.cursors.DictCursor)
else:
dbMySQL_Cursor = conn.cursor()
self.dbMySQL_Cursor = dbMySQL_Cursor
def closeCursor(self):
self.dbMySQL_Cursor.close()
#=============================================================================
# QUERY FUNCTIONS
#------------------------------------------------------------------------------
def runQueryNoCursor(qryStr, conn, dict_flag=True):
dbMySQL_Cursor = conn.getCursor(dict_flag)
qry_res =runQueryFnc(qryStr, dbMySQL_Cursor.dbMySQL_Cursor)
dbMySQL_Cursor.closeCursor()
return qry_res
#------------------------------------------------------------------------------
def runQueryFnc(qryStr, dbMySQL_Cursor):
qry_res = {}
qry_res['rows'] = dbMySQL_Cursor.execute(qryStr)
qry_res['result'] = copy.deepcopy(dbMySQL_Cursor.fetchall())
qry_res['messages'] = copy.deepcopy(dbMySQL_Cursor.messages)
qry_res['query_str'] = qryStr
return qry_res
#=============================================================================
# USAGES
qry = 'DROP DATABASE IF EXISTS database_of_armaments'
dbConn = dbMySQL_Connection(**c.creds)
def dbConnRunQuery():
# Does not trap an exception; warning displayed to standard error.
try:
dbConn.runQuery(qry)
except:
print "dbConn.runQuery() caught an exception."
def dbConnCursorExecute():
# Does not trap an exception; warning displayed to standard error.
dbConn.getCursor() # try/except block does catches error without this
try:
dbConn.dbMySQL_Cursor.dbMySQL_Cursor.execute(qry)
except Exception, e:
print "dbConn.dbMySQL_Cursor.execute() caught an exception."
print repr(e)
def funcRunQueryNoCursor():
# Does not trap an exception; no warning displayed
try:
res = runQueryNoCursor(qry, dbConn)
print 'Try worked. %s' % res
except Exception, e:
print "funcRunQueryNoCursor() caught an exception."
print repr(e)
#=============================================================================
if __name__ == '__main__':
print '\n'
print 'EXAMPLE -- dbConnRunQuery()'
dbConnRunQuery()
print '\n'
print 'EXAMPLE -- dbConnCursorExecute()'
dbConnCursorExecute()
print '\n'
print 'EXAMPLE -- funcRunQueryNoCursor()'
funcRunQueryNoCursor()
print '\n'
