Python Logging and Handling

[phillyfa]

Hello,

I typically write small programs for Python and never attempted to use logging or exception handling. This is all new to me, but with this program I'm currently writing I would like to incorporate error handling and file logging.

I'm receiving the following error when attempting to do so:

Error:
Traceback (most recent call last):
  File "C:/Users/AnelliaF/.PyCharmCE2019.3/config/scratches/sql_create_csv_w_logging.py", line 15, in main
    conn = pyodbc.connect('Driver={SQL Server};'
pyodbc.OperationalError: ('08001', '[08001] [Microsoft][ODBC SQL Server Driver][DBNETLIB]SQL Server does not exist or access denied. (17) (SQLDriverConnect); [08001] [Microsoft][ODBC SQL Server Driver][DBNETLIB]ConnectionOpen (Connect()). (53)')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:/Users/AnelliaF/.PyCharmCE2019.3/config/scratches/sql_create_csv_w_logging.py", line 45, in <module>
    main()
  File "C:/Users/AnelliaF/.PyCharmCE2019.3/config/scratches/sql_create_csv_w_logging.py", line 20, in main
    print("Error %d: %s" % (e.args[0], e.args[1]))
TypeError: %d format: a number is required, not str

Here is the code:

import pyodbc
import csv
import logging
import sys

def main():
    #logging.basicConfig(filename='c:\\temp\\test.log', format='%(filename)s: %(message)s', level=logging.DEBUG)
    # Configure logging
    logging.basicConfig(filename='c:\\temp\\test.log', format='%(asctime)s: %(message)s', level=logging.DEBUG)
    logger = logging.getLogger()

    logger.info('Connecting to database...')
    # Create connection object that represents the database
    try:
        conn = pyodbc.connect('Driver={SQL Server};'
                              'Server=MJ;'
                              'Database=AdventureWorks2012;'
                              'Trusted_Connection=yes;')
    except pyodbc.Error as e:
        print("Error %d: %s" % (e.args[0], e.args[1]))
        sys.exit(1)

    logger.info('Selecting records...')
    cursor = conn.cursor()
    script = """
    SELECT TOP 10 * FROM person.person
    """
    cursor.execute(script)

    logger.info('Writing to CSV file...')
    with open("c:\\temp\\csv_from_sql.csv", 'w') as csv_from_sql:
        csv_writer = csv.writer(csv_from_sql, delimiter=',', lineterminator='\n')
        # Write field name header line
        csv_writer.writerow([i[0] for i in cursor.description])
        # Write data rows
        # Use enumerate() method to count rows
        for row_num, row in enumerate(cursor, start = 1):
            csv_writer.writerow(row)

    logger.debug(f'Number of records: {row_num}')
    #print(f'Number of rows: {row_num}')
    logger.info('Finished writing file')

if __name__ == '__main__':
    main()

I have two questions:

1 - It seems my exception is failing, but unsure why?
2 - Is there anywhere else in the code I should attempt to add logging and handling?

Thanks,
Frank

[buran]

with %d string format code you need to pass a number, you pass a string instead, thus the TypeError

>>> spam = 100
>>> eggs  = '200'
>>> print('%d' %spam)
100
>>> print('%d' %eggs)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: %d format: a number is required, not str

As a side note, not relevant to error you get, instead of old-style formatting, use str.format() method or f-strings

[phillyfa]

I went with new style format as you stated:

print("Error {}: {}".format(e.args[0], e.args[1]))

Error:
Error 08001: [08001] [Microsoft][ODBC SQL Server Driver][DBNETLIB]SQL Server does not exist or access denied. (17) (SQLDriverConnect); [08001] [Microsoft][ODBC SQL Server Driver][DBNETLIB]ConnectionOpen (Connect()). (53)

It worked.

Any other areas in the code should I place logging or handling? Or is there other ways to handle the exceptions?