如何在Python中的函数入口，内部和出口处进行日志记录 [英] How to do logging at function entry, inside and exit in Python

问题描述

我希望能够使用Python日志记录工具在我的代码中进行简单且一致的日志记录.

I'd like to be able to do simple and consistent logging in my code using the Python logging facility.

我能够执行以下操作:

1. 我希望所有现有/将来的模块和功能都具有"Entering ..."和"Done ..."日志消息.
2. 我不想在每个函数定义中为定义日志记录参数(显示在don't want to add everywhere下)添加相同的代码段.
3. 我希望log.info(...) etc构造可以在我在项目层次结构中定义的任何功能中使用.

1. I'd like all existing/future module and functions to have "Entering ..." and "Done ..." log messages.
2. I don't want to add the same code snippet to defining logging parameters (shown below don't want to add everywhere) in every function definition.
3. I want the log.info(...) etc constructs to work in any function I define in the project hierarchy.

什么是行不通的/我不知道该怎么做:

1. 我想避免在我编写的每个现有/新模块中定义相同的@log装饰器.

1. I'd like to avoid defining the same @log decorator in every existing/new module that I write.

# don't want to add everywhere
FORMAT = '%(asctime)s - %(name)-20s - %(levelname)-5s - %(message)s'
LEVEL = logging.DEBUG
logging.basicConfig(format=FORMAT, level=LEVEL)
log = logging.getLogger(__name__)

我的Flask项目中的示例代码:

# app/__init__.py
from a import b  # various other imports required for app
import logging
FORMAT = '%(asctime)s - %(name)-20s - %(levelname)-5s - %(message)s'
LEVEL = logging.DEBUG
logging.basicConfig(format=FORMAT, level=LEVEL)
log = logging.getLogger(__name__)
# ... various other app init code
from app import views, models

#app/views.py
from c import d  # various other imports required for the module

def logger(fn):
    from functools import wraps
    import inspect
    @wraps(fn)
    def wrapper(*args, **kwargs):
        global log
        log = logging.getLogger(inspect.stack()[1][3])
        log.info('About to run %s' % fn.__name__)

        out = apply(fn, args, kwargs)

        log.info('Done running %s' % fn.__name__)
        # Return the return value
        return out
    return wrapper

    @app.route('/this_func')
    @logger
    def this_func():
        log.info('I am doing logging without having to do bunch of definitions.')
        # some more code

    @app.route('/that_func')
    @logger
    def that_func():
        log.info('Yet more logging without having to do bunch of definitions.')
        log.info('I can simply refer to the log object and be done with it.')
        # some more code

推荐答案

对我有用的最终设置如下:

The final setup that worked for me was the following:

# At the beginning of every .py file in the project
def logger(fn):
    from functools import wraps
    import inspect
    @wraps(fn)
    def wrapper(*args, **kwargs):
        log = logging.getLogger(fn.__name__)
        log.info('About to run %s' % fn.__name__)

        out = apply(fn, args, kwargs)

        log.info('Done running %s' % fn.__name__)
        # Return the return value
        return out
    return wrapper

# Do the following section only in application's app/__init__.py
# Other files will pick it up from here.
FORMAT = '%(asctime)s - %(name)s - %(levelname)s - %(funcName)s - %(message)s'

# Change logging LEVEL according to debugging needs.
# Probably better to read this from a config or a launch parameter.
LEVEL = logging.DEBUG

logging.basicConfig(format=FORMAT, level=LEVEL)
# Up to here only for app/__init__.py

# This section again at the beginning of every .py file
log = logging.getLogger(__name__)
log.info('Entered module: %s' % __name__)

现在，在模块中的每个函数定义中添加一个@logger装饰器:

Now, add a @logger decorator to every function definition in the module:

@logger
def do_something():
    print('doing really useful stuff.')

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