Make logging simple, log even exception that you forgot to catch
Project description
Logger_tt
Make configuring logging simpler and log even exceptions that you forgot to catch.
Install
- From PYPI:
pip install logger_tt
- From Github: clone or download this repo then
python setup.py install
Overview:
In the most simple case, add the following code into your main python script of your project:
from logger_tt import setup_logging
setup_logging()
Then from any of your modules, you just need to get a logger
and start logging.
from logging import getLogger
logger = getLogger(__name__)
logger.debug('Module is initialized')
logger.info('Making connection ...')
This will provide your project with the following default log behavior:
-
log file: Assume that your
working directory
isproject_root
, log.txt is stored at yourproject_root/logs/
folder. If the log path doesn't exist, it will be created. The log file is time rotated at midnight. A maximum of 15 dates of logs will be kept. This log file'slevel
isDEBUG
.
The log format is[%(asctime)s] [%(name)s %(levelname)s] %(message)s
where time is%Y-%m-%d %H:%M:%S
.
Example:[2020-05-09 00:31:33] [myproject.mymodule DEBUG] Module is initialized
-
console: log with level
INFO
and above will be printed tostdout
of the console.
The format for console log is simpler:[%(asctime)s] %(levelname)s: %(message)s
.
Example:[2020-05-09 00:31:34] INFO: Making connection ...
-
urllib3
logger: this ready-made logger is to silent unwanted messages fromrequests
library. -
suppressed logger:
exchangelib
. This sets logging level ofexchangelib
logger toWARNING
.
This is another ways to silent unwanted messages from other module, read below for details. -
root
logger: if there is no logger initialized in your module, this logger will be used with the above behaviors. This logger is also used to log uncaught exception in your project. Example:
raise RecursionError
# log.txt
[2020-05-31 19:16:01] [root ERROR] Uncaught exception
Traceback (most recent call last):
File "D:/MyProject/Echelon/eyes.py", line 13, in <module>
raise RecursionError
=> var_in = Customer(name='John', member_id=123456)
=> arg = (456, 789)
=> kwargs = {'my_kw': 'hello', 'another_kw': 'world'}
RecursionError
- context logging: When an exception occur, variables used in the line of error are also logged.
If the line of error israise {SomeException}
, then local variables are also logged.
To always log full local variables, passfull_context=True
tosetup_logging
.
Usage:
All configs are done through setup_logging
function:
setup_logging(config_path="", log_path="",
capture_print=False, strict=False, guess_level=False,
full_context=False,
suppress_level_below=logging.WARNING)
-
You can overwrite the default log path with your own as follows:
setup_logging(log_path='new/path/to/your_log.txt')
-
You can config your own logger and handler by providing either
yaml
orjson
config file as follows:setup_logging(config_path='path/to/.yaml_or_.json')
Without providing a config file, the default config file with the above default log behavior is used. You could copy
log_conf.yaml
orlog_conf.json
shipped with this package to start making your version.Warning: To process
.yaml
config file, you needpyyaml
package:pip install pyyaml
-
Capture stdout:
If you have an old code base with a lot of
print(msg)
orsys.stdout.write(msg)
and don't have access or time to refactor them into something likelogger.info(msg)
, you can capture thesemsg
and log them to file, too.To capture only
msg
that is printed out byprint(msg)
, simply do as follows:setup_logging(capture_print=True)
Example:
print('To be or not to be') sys.stdout.write('That is the question')
# log.txt [2020-05-09 11:42:08] [PrintCapture INFO] To be or not to be
Yes,
That is the question
is not captured. Some libraries may directly usesys.stdout.write
to draw on the screen (eg. progress bar) or do something quirk. This kind of information is usually not useful for users. But when you do need it, you can capture it as follows:setup_logging(capture_print=True, strict=True)
Example:
sys.stdout.write('The plane VJ-723 has been delayed') sys.stdout.write('New departure time has not been scheduled')
# log.txt [2020-05-09 11:42:08] [PrintCapture INFO] The plane VJ-723 has been delayed [2020-05-09 11:42:08] [PrintCapture INFO] New departure time has not been scheduled
As you have seen, the log level of the captured message is
INFO
. What if the code base prints something likeAn error has occurred. Abort operation.
and you want to log it asError
? Just addguess_level=True
tosetup_logging()
.setup_logging(capture_print=True, guess_level=True)
Example:
print('An error has occurred. Abort operation.') print('A critical error has occurred during making request to database')
# log.txt [2020-05-09 11:42:08] [PrintCapture ERROR] An error has occurred. Abort operation. [2020-05-09 11:42:08] [PrintCapture CRITICAL] A critical error has occurred during making request to database
Note: Capturing stdout ignores messages of
blank line
. That means messages like\n\n
or\nTo day is a beautiful day\n
will be logged as is. -
Exception logging:
Consider the following error code snippet:
API_KEY = "asdjhfbhbsdf82340hsdf09u3ionf98230234ilsfd" TIMEOUT = 60 class MyProfile: def __init__(self, name): self.my_boss = None self.name = name def my_faulty_func(my_var, *args, **kwargs): new_var = 'local scope variable' me = MyProfile('John Wick') boss = MyProfile('Winston') me.my_boss = boss print(f'Information: {var} and {me.my_boss.name}' ' at {me.my_boss.location} with {API_KEY}') if __name__ == '__main__': cpu_no = 4 max_concurrent_processes = 3 my_faulty_func(max_concurrent_processes, 'ryzen 7', freq=3.4)
In our hypothetical code above,
print
function will raise an exception. This exception, by default, will not only be logged but also analyzed with objects that appeared in the line:[2020-06-06 09:36:01] ERROR: Uncaught exception: Traceback (most recent call last): File "D:/MyProject/AutoBanking/main.py", line 31, in <module> my_faulty_func(max_concurrent_processes, 'ryzen 7', freq=3.4) |-> my_faulty_func = <function my_faulty_func at 0x0000023770C6A288> |-> max_concurrent_processes = 3 File "D:/MyProject/AutoBanking/main.py", line 25, in my_faulty_func print(f'Information: {var} and {me.my_boss.name}' ' at {me.my_boss.location} with {API_KEY}') |-> me.my_boss.name = 'Winston' |-> me.my_boss.location = '!!! Not Exists' |-> (outer) API_KEY = 'asdjhfbhbsdf82340hsdf09u3ionf98230234ilsfd' NameError: name 'var' is not defined
Note: look at the
print(f'Information...
line,logger-tt
print this error line different from normal python traceback! With normal traceback, multi-line python statement has its only first line printed out. Withlogger-tt
, full statement is grabbed for you.For each level in the stack, any object that appears in the error line is shown with its
readable representation
. This representation may not necessarily be__repr__
. The choice between__str__
and__repr__
are as follows:__str__
:__str__
is present and the object class's__repr__
is default with<class name at Address>
.__repr__
:__str__
is present but the object class's__repr__
is anything else, such asClassName(var=value)
.
Also, when__str__
is missing, even if__repr__
is<class name at Address>
, it is used.
Currently, if an object doesn't exist and is directly accessed, as
var
in this case, it will not be shown up. But if it is attribute accessed with dot.
, aslocation
inme.my_boss.location
, then its value is an explicit string'!!! Not Exists'
.As you may have noticed, a variable
API_KEY
has its name prefixed withouter
.
This tells you that the variable is defined in the outer scope, not local.More often than not, only objects in the error line are not sufficient to diagnose what has happened. You want to know what the inputs of the function were. You want to know what the intermediate calculated results were. You want to know other objects that appeared during runtime, not only local but also outer scope. In other words, you want to know the full context of what has happened.
logger-tt
is here with you:setup_logging(full_context=True)
With the above hypothetical code snippet, the error log becomes the following:
[2020-06-06 10:35:21] ERROR: Uncaught exception: Traceback (most recent call last): File "D:/MyProject/AutoBanking/main.py", line 31, in <module> my_faulty_func(max_concurrent_processes, 'ryzen 7', freq=3.4) |-> my_faulty_func = <function my_faulty_func at 0x0000019E3599A288> |-> max_concurrent_processes = 3 => __name__ = '__main__' => __doc__ = None => __package__ = None => __loader__ = <_frozen_importlib_external.SourceFileLoader object at 0x0000019E35840E48> => __spec__ = None => __annotations__ = {} => __builtins__ = <module 'builtins' (built-in)> => __file__ = 'D:/MyProject/AutoBanking/main.py' => __cached__ = None => setup_logging = <function setup_logging at 0x0000019E35D111F8> => getLogger = <function getLogger at 0x0000019E35BC7C18> => logger = <Logger __main__ (DEBUG)> => API_KEY = 'asdjhfbhbsdf82340hsdf09u3ionf98230234ilsfd' => TIMEOUT = 60 => MyProfile = <class '__main__.MyProfile'> => cpu_no = 4 File "D:/MyProject/AutoBanking/main.py", line 25, in my_faulty_func print(f'Information: {var} and {me.my_boss.name} at {me.my_boss.location} with {API_KEY}') |-> me.my_boss.name = 'Winston' |-> me.my_boss.location = '!!! Not Exists' |-> (outer) API_KEY = 'asdjhfbhbsdf82340hsdf09u3ionf98230234ilsfd' => my_var = 3 => args = ('ryzen 7',) => kwargs = {'freq': 3.4} => new_var = 'local scope variable' => me = <__main__.MyProfile object at 0x0000019E35D3BA48> => boss = <__main__.MyProfile object at 0x0000019E35D3B9C8> NameError: name 'var' is not defined
Additional objects that not appear in the error line are prefixed with
=>
. -
try-except
exception logging:exception context
logging also applies fortry-except
block. This means that if you calllogger.exception()
insideexcept
block, you would have all variables' value at the line of exception. For example,def my_faulty_func(): a = 10 b = 0 c = a/b return c def my_main(): try: my_faulty_func() except Exception as e: logger.exception('some error has occured') print('Clean up resource') my_main()
Then the log will show up as follows:
[2020-06-12 21:37:00] ERROR: some error has occured Traceback (most recent call last): File "D:/MyProject/exception_log.py", line 19, in my_main my_faulty_func() |-> my_faulty_func = <function my_faulty_func at 0x000001875DD4B168> File "D:/MyProject/exception_log.py", line 13, in my_faulty_func c = a / b |-> a = 10 |-> b = 0 ZeroDivisionError: division by zero Clean up resource
Note: As in python's logging document,
logger.exception()
should only be called from an exception handler, eg. insideexcept
block.You don't need to pass
exception object
tologger.exception()
. It already knows how to get a traceback internally. This enable you to pass any string in as a hint or a short description of what may have happened.
Otherwise, passingexception object
, aslogger.exception(e)
, will cause the first line of error report to be the message of exception. In the case of the above example, it would be come[2020-06-12 21:37:00] ERROR: division by zero
. -
Silent unwanted logger:
Third party modules also have logger and their messages are usually not related to your code. A bunch of unwanted messages may hide the one that come from your own module. To prevent that and also reduce log file size, we need to silent unwanted loggers.
There are two ways to silent a logger with config file:
-
Create a new logger: in
logger
section of config file, add a new logger whose name is the same with the one you want to silent. Set it level toWARNING
or above. If you addhandlers
, you should also setpropagate
tono
orFalse
. Otherwise, the same message may be logged multiple times. Ex:urllib3: level: WARNING handlers: [console, error_file_handler] propagate: no
Above setting only allow messages with level
WARNING
and above to be processed. Usually that is enough to silent most of unwanted messages. If you need to silent more messages, tryERROR
orCRITICAL
. -
Add logger's name to
suppress list
: Then a new logger with level default toWARNING
will be automatically created for you. Ex:suppress: [exchangelib, urllib3]
If you need to suppress at even higher level, use
suppress_level_below
insetup_logging
. For example suppress any message belowERROR
level that comes from loggers insuppress list
:setup_logging(suppress_level_below=logging.ERROR)
-
Sample config:
-
Yaml format:
log_config.yaml:
version: 1 disable_existing_loggers: False formatters: simple: format: "[%(asctime)s] [%(name)s %(levelname)s] %(message)s" datefmt: "%Y-%m-%d %H:%M:%S" brief: { format: "[%(asctime)s] %(levelname)s: %(message)s" datefmt: "%Y-%m-%d %H:%M:%S" handlers: console: class: logging.StreamHandler level: INFO formatter: simple stream: ext://sys.stdout error_file_handler: class: logging.handlers.TimedRotatingFileHandler level: DEBUG formatter: simple filename: logs/log.txt backupCount: 15 encoding: utf8 when: midnight loggers: urllib3: level: WARNING handlers: [console, error_file_handler] propagate: no root: level: DEBUG handlers: [console, error_file_handler] suppress: [exchangelib]
2. Json format:
log_config.json:
{
"version": 1,
"disable_existing_loggers": false,
"formatters": {
"simple": {
"format": "[%(asctime)s] [%(name)s %(levelname)s] %(message)s",
"datefmt": "%Y-%m-%d %H:%M:%S"
},
"brief": {
"format": "[%(asctime)s] %(levelname)s: %(message)s",
"datefmt": "%Y-%m-%d %H:%M:%S"
}
},
"handlers": {
"console": {
"class": "logging.StreamHandler",
"level": "INFO",
"formatter": "brief",
"stream": "ext://sys.stdout"
},
"error_file_handler": {
"class": "logging.handlers.TimedRotatingFileHandler",
"level": "DEBUG",
"formatter": "simple",
"filename": "logs/log.txt",
"backupCount": 15,
"encoding": "utf8",
"when": "midnight"
}
},
"loggers": {
"urllib3": {
"level": "ERROR",
"handlers": ["console", "error_file_handler"],
"propagate": false
}
},
"root": {
"level": "DEBUG",
"handlers": ["console", "error_file_handler"]
},
"suppress": ["exchangelib"]
}
changelog
1.4.0
- Add an extra field
suppress
in config file. Any logger's name appeared in this list will have its messages suppressed.
1.3.2
- change extended ascii dash
─
to normal dash-
so that it is displayed consistently in different encoding
1.3.1
- change extended ascii vertical bar
├
to normal bar|
so that it is displayed consistently in different encoding
1.3.0
- Exception analyzing now fetch full multi-line python statement.
This means that variables lie at seconds and below of the same statement can also be seen
without the need of
full_context=True
.
1.2.1
- Extend logging context to
logger.exception()
as well. Now you can dotry-except
a block of code and still have a full context at error line.
1.2.0
- Add logging context for uncaught exception. Now automatically log variables surrounding the error line, too.
- Add test cases for logging exception
1.1.1
- Fixed typos and grammar
- Add config file sample to README
- using full name
log_config.json
instead oflog_conf.json
, the same for yaml file - add test cases for
capture print
1.1.0
- Add
capture print
functionality withguess level
for the message.
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