Exception Hanlding of Lists

[anelliaf]

Hello,

I'm writing a program that will list available databases to a user based on their tnsnames.ora and then allow them to make a connection to one available. I want to return a message if they attempt to use something other than what's available in the list.

Here is a snippet of the code:

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def db_menu():     os.chdir(r'c:\temp')  # move to tns directoy; raw string       tns = open('tnsnames.ora', 'r')  # open file in read mode     sList = tns.read()  # read file into string     sList = re.sub("#.*\n", "", sList)  # strip all comments     sList = re.sub("\(.*\n", "", sList)  # remove "(" to end of line     sList = re.sub("\)", "", sList)  # clean up ")"     sList = re.sub(" ", "", sList)  # remove spaces     sList = re.sub("\n", "", sList)  # remove carriage returns     sList = re.sub("=$", "", sList)  # remove last "="     sList = sList.split("=")  # create list     tns.close()       print('\nAvailable Databases: ')     for i in sList:         print(i)   # Database Login def db_login():     db_menu()     while True:         try:             # Input username and password               uname = input('\nEnter username: ')             pw = getpass.getpass(prompt='Enter password: ')             db = input('Enter database: ')             conn_str = u'%s/%s@%s' % (uname, pw, db)                            # connection string             conn = cx_Oracle.connect(conn_str)                                  # connection to database             cur = conn.cursor()                                                 # parameter to access cursor method             q_str = "select * from global_name"                                 # create a query string             cur.execute(q_str)                                                  # pass to cursor method               for row in cur:                 print("\nConnected to: {}".format(row))             else:                 break           except cx_Oracle.DatabaseError as e:             error, = e.args             print("\nInvalid username/password.  Please try again.\n")

Do I need to add another exception or would it be something of an if/else statement so they can continue to login once the correct database is entered?

Thanks!

[nilamo]

I'd move the file handling to it's own function, so it would be fine to call db_menu() multiple times. Then I'd write a while loop that just kept asking for a valid database to connect to. Something like:

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def get_available_databases():     os.chdir('c:/temp')  # move to tns directoy; raw string     # open file in read mode     with open('tnsnames.ora', 'r') as tns:         sList = tns.read()  # read file into string         sList = re.sub("#.*\n", "", sList)  # strip all comments         sList = re.sub("\(.*\n", "", sList)  # remove "(" to end of line         sList = re.sub("\)", "", sList)  # clean up ")"         sList = re.sub(" ", "", sList)  # remove spaces         sList = re.sub("\n", "", sList)  # remove carriage returns         sList = re.sub("=$", "", sList)  # remove last "="         sList = sList.split("=")  # create list         return sList   def db_menu(db_names):     print('\nAvailable Databases: ')     for i in db_names:         print(i)    def select_db_name(available_db_names):     while True:         db_menu(available_db_names)         selection = input('Enter database: ')         if selection in available_db_names:             return selection         print("Database unavailable.")   # Database Login def db_login():     available_db_names = get_available_databases()     while True:         try:             # Input username and password                uname = input('\nEnter username: ')             pw = getpass.getpass(prompt='Enter password: ')             db = select_db_name(available_db_names)             conn_str = u'%s/%s@%s' % (uname, pw, db)                            # connection string             conn = cx_Oracle.connect(conn_str)                                  # connection to database             cur = conn.cursor()                                                 # parameter to access cursor method             q_str = "select * from global_name"                                 # create a query string             cur.execute(q_str)                                                  # pass to cursor method                for row in cur:                 print("\nConnected to: {}".format(row))             else:                 break            except cx_Oracle.DatabaseError as e:             error, = e.args             print("\nInvalid username/password.  Please try again.\n")

[anelliaf]

This worked! Great advice and awesome code! Much appreciated!