Assertions
It is a sanity check to make sure the code is not doing something obviously
wrong. These are done with assert statements. If the sanity check fails,
then an assertError exception is raised.
Logging
Logging is used to debug the code. It can print information, warnings, debugging and errors while the script is running.
Using the logging module
To set the logging messages the following syntax is used:
import logging
logging.basicConfig(
filename='my_log.txt',
level=logging.DEBUG,
format=' %(asctime)s - %(levelname)s - %(message)s'
)
The basicConfig parameters do the following:
- filename: the file to store the logs (optional)
- level: priority of message to show (starting from)
- format: how to show the log
- %(asctime)s: date time
- %(levelname)s: logging level
- %(message)s: message specified in the log
Logging levels
There are several types of logging:
| Logging function | Description |
|---|---|
logging.debug() | Lowest level. Used for small details, mostly when diagnosing problems |
logging.info() | Used to record information on general events, confirm that things are working as expected |
logging.warning() | Indicate potential problem that doesn’t prevent the program from working |
logging.error() | Used to record an error that caused the program to fail |
logging.critical() | Highest leve, used to indicate fatal aerror that has caused or is about to crash the program |
Disable logging
Using logging.disable(logging.CRITICAL) will disable the logs starting from the
level passed as an argument. This is useful when the code has been tested and
we don’t want all the logs to be passed.
Raise exception
To raise an exception the code raise Exception('Error message') can be used,
it will interrupt the code and raise a specific error message.