python-devlog 1.2

No more logging in your code business logic with decorators

devlog

No more logging in your code business logic with python decorators.

Logging is a very powerful tool for debugging and monitoring your code. But if you are often ommitting logging statements, you will quickly find yourself overcrowded with logging statements.

Fortunately, you could avoid this by using the python decorator. This library provide easy logging for your code without stealing readability and maintainability. Furthermore, it also provides stack trace to get full local variable on the function.

How to use:

To use this library, you just need to add the decorator to your function. Depending on when you want to log, you can use the decorator as below:

import logging

from devlog import log_on_start, log_on_end, log_on_error

logging.basicConfig(level=logging.DEBUG)


@log_on_start
@log_on_end
def test_1(a, b):
    return a + b


@log_on_error
def test_2(a, b):
    return a / b


if __name__ == '__main__':
    test_1(1, b=2)
    # INFO:__main__:Start func test_1 with args (1,), kwargs {'b': 2}
    # INFO:__main__:Successfully run func test_1 with args (1,), kwargs {'b': 2}

    test_2("abc", "def")
    # ERROR:__main__:Error in func test_2 with args ('abc', 'def'), kwargs {}
    # 	unsupported operand type(s) for /: 'str' and 'str'.

What devlog can do for you

Decorators

devlog provides three different decorators:

• LogOnStart: Log when the function is called.
• LogOnEnd: Log when the function is finished.
• LogOnError: Log when the function is finished with error.

Use variables in messages

The message given to decorators are treated as a format string which takes the function arguments as the format arguments.

The following example shows how to use variables in messages:

import logging

from devlog import log_on_start

logging.basicConfig(level=logging.DEBUG)


@log_on_start(logging.INFO, 'Start func {callable.__name__} with args {args}, kwargs {kwargs}')
def hello(name):
    print("Hello, {}".format(name))


if __name__ == "__main__":
    hello("World")

Which will print: INFO:__main__:Start func hello with args ('World',), kwargs {}

Documentation

format variables

The following variables are available in the format string:

Default variable name	Description	LogOnStart	LogOnEnd	LogOnError
callable	The function object	Yes	Yes	Yes
args/kwargs	The arguments, key arguments passed to the function	Yes	Yes	Yes
result	The return value of the function	No	Yes	No
error	The error object if the function is finished with error	No	No	Yes

base arguments

Available arguments in all decorators are:

Arguments	Description
logger	The logger object. If no logger is given, the devlog will create a logger object with the name of the module where the function is defined. Default is logging.getLogger(callable.__name__)
handler	A custom log handler object. Only available if no logger object is given,
args_kwargs	Set true if the message format using args, kwargs format or false to use function parameter name format. Default True
callable_format_variable	The format variable to use for callable. Default is callable
trace_stack	Set to True if you want to get the full stack trace. Default is False or capture_local
capture_locals	Set to True if you want to get the local variable of the function. Default is False (or trace_stack on log_on_error decorator)
include_decorator	Set to True if you want to include the devlog libray on the stack. Default is False

log_on_start

Arguments	Description
level	The level of the log message. Default is logging.INFO
message	The message to log. Could using {args} {kwargs} or function parameter name but not both. Default is Start func {callable.__name__} with args {args}, kwargs {kwargs}

log_on_end

Arguments	Description
level	The level of the log message. Default is logging.INFO
message	The message to log. Could using {args} {kwargs} or function parameter name but not both. Default is Successfully run func {callable.__name__} with args {args}, kwargs {kwargs}
result_format_variable	The format variable to use for reference the return from callable. Default is result

log_on_error

Arguments	Description
level	The level of the log message. Default is logging.ERROR
message	The message to log. Could using {args} {kwargs} or function parameter name but not both. Default is Successfully run func {callable.__name__} with args {args}, kwargs {kwargs}
on_exceptions	A tuple containing exception classes or a single exception, which should get caught and trigger the logging. Default is tuple() (All exception will get caught)
reraise	Control whether the exception should be reraised after logging. Default is True
exception_format_variable	The format variable to use for reference the exception raised in callable. Default is error

Extras

Stack trace

The stack trace configuration.

method	Description
set_stack_start_frames	The number of frames to skip at the start (positive value). Default is 0
set_stack_removal_frames	The number of frames to remove from the back of the stack trace (positive value). Default is 6 (the last 6 frame usually from the devlog module)

Custom exception hook

Override the default exception hook with a custom function.

import devlog

devlog.system_excepthook_overwrite()  # Overwrite the default exception hook

This will replace the sys.excepthook with the devlog.excepthook.

Arguments	Description
out_file	The path to the file to write the log. Default is crash.log