better-exceptions
Pretty and more helpful exceptions in Python, automatically.
Usage
Install better_exceptions
via pip:
pip install better_exceptions
And set the BETTER_EXCEPTIONS
environment variable to any value:
export BETTER_EXCEPTIONS=1 # Linux / OSX
setx BETTER_EXCEPTIONS 1 # Windows
That's it!
Python REPL (Interactive Shell)
In order to use better_exceptions
in the Python REPL, first install the package (as instructed above) and run:
$ python -m better_exceptions
Type "help", "copyright", "credits" or "license" for more information.
(BetterExceptionsConsole)
>>>
in order to drop into a better_exceptions
-enabled Python interactive shell.
Advanced Usage
If you want to allow the entirety of values to be outputted instead of being truncated to a certain amount of characters:
import better_exceptions
better_exceptions.MAX_LENGTH = None
While using better_exceptions
in production, do not forget to unset the BETTER_EXCEPTIONS
variable to avoid leaking sensitive data in your logs.
Use with unittest
If you want to use better_exceptions
to format unittest
's exception output, you can use the monkey patch below:
import sys
import unittest
import better_exceptions
def patch(self, err, test):
lines = better_exceptions.format_exception(*err)
if sys.version_info[0] == 2:
return u"".join(lines).encode("utf-8")
return "".join(lines)
unittest.result.TestResult._exc_info_to_string = patch
Note that this uses an undocumented method override, so it is not guaranteed to work on all platforms or versions of Python.
Django Usage
In settings.py
, add your new class to the MIDDLEWARE
setting and update your logging configuration:
# ...
MIDDLEWARE = [
# ...
"better_exceptions.integrations.django.BetterExceptionsMiddleware",
]
# ...
from better_exceptions.integrations.django import skip_errors_filter
# if you don't want to override LOGGING because you want to change the default,
# you can vendor Django's default logging configuration and update it for
# better-exceptions. the default for Django 3.1.4 can be found here:
# https://github.com/django/django/blob/3.1.4/django/utils/log.py#L13-L63
LOGGING = {
'version': 1,
'disable_existing_loggers': False,
'filters': {
'skip_errors': {
'()': 'django.utils.log.CallbackFilter',
'callback': skip_errors_filter,
}
},
'handlers': {
'console': {
'level': 'INFO',
# without the 'filters' key, Django will log errors twice:
# one time from better-exceptions and one time from Django.
# with the 'skip_errors' filter, we remove the repeat log
# from Django, which is unformatted.
'filters': ['skip_errors'],
'class': 'logging.StreamHandler',
}
},
'loggers': {
'django': {
'handlers': [
'console',
],
}
}
}
example output:
Troubleshooting
If you do not see beautiful exceptions, first make sure that the environment variable does exist. You can try echo $BETTER_EXCEPTIONS
(Linux / OSX) or echo %BETTER_EXCEPTIONS%
(Windows). On Linux and OSX, the export
command does not add the variable permanently, you will probably need to edit the ~/.profile
file to make it persistent. On Windows, you need to open a new terminal after the setx
command.
Check that there is no conflict with another library, and that the sys.excepthook
function has been correctly replaced with the better_exceptions
's one. Sometimes other components can set up their own exception handlers, such as the python3-apport
Ubuntu package that you may need to uninstall.
Make sure that you have not inadvertently deleted the better_exceptions_hook.pth
file that should be in the same place as the better_exceptions
folder where all of your Python packages are installed. Otherwise, try re-installing better_exceptions
.
You can also try to manually activate the hook by adding import better_exceptions; better_exceptions.hook()
at the beginning of your script.
Finally, if you still can not get this module to work, open a new issue by describing your problem precisely and detailing your configuration (Python and better_exceptions
versions, OS, code snippet, interpreter, etc.) so that we can reproduce the bug you are experiencing.
License
Copyright © 2017, Josh Junon. Licensed under the MIT license.