Python 终极调试指南

import logginglogging.basicConfig(    filename='application.log',    level=logging.WARNING,    format= '[%(asctime)s] {%(pathname)s:%(lineno)d} %(levelname)s - %(message)s',    datefmt='%H:%M:%S')logging.error("Some serious error occurred.")logging.warning('Function you are using is deprecated.')

[12:52:35] {<stdin>:1} ERROR - Some serious error occurred.[12:52:35] {<stdin>:1} WARNING - Function you are using is deprecated.

version: 1disable_existing_loggers: trueformatters:  standard:    format: "[%(asctime)s] {%(pathname)s:%(lineno)d} %(levelname)s - %(message)s"    datefmt: '%H:%M:%S'handlers:  console:  # handler which will log into stdout    class: logging.StreamHandler    level: DEBUG    formatter: standard  # Use formatter defined above    stream: ext://sys.stdout  file:  # handler which will log into file    class: logging.handlers.RotatingFileHandler    level: WARNING    formatter: standard  # Use formatter defined above    filename: /tmp/warnings.log    maxBytes: 10485760 # 10MB    backupCount: 10    encoding: utf8root:  # Loggers are organized in hierarchy - this is the root logger config  level: ERROR  handlers: [console, file]  # Attaches both handler defined aboveloggers:  # Defines descendants of root logger  mymodule:  # Logger for "mymodule"    level: INFO    handlers: [file]  # Will only use "file" handler defined above    propagate: no  # Will not propagate logs to "root" logger

import yamlfrom logging import configwith open("config.yaml", 'rt') as f:    config_data = yaml.safe_load(f.read())    config.dictConfig(config_data)

from functools import wraps, partialimport loggingdef attach_wrapper(obj, func=None):  # Helper function that attaches function as attribute of an object    if func is None:        return partial(attach_wrapper, obj)    setattr(obj, func.__name__, func)    return funcdef log(level, message):  # Actual decorator    def decorate(func):        logger = logging.getLogger(func.__module__)  # Setup logger        formatter = logging.Formatter(            '%(asctime)s - %(name)s - %(levelname)s - %(message)s')        handler = logging.StreamHandler()        handler.setFormatter(formatter)        logger.addHandler(handler)        log_message = f"{func.__name__} - {message}"        @wraps(func)        def wrapper(*args, **kwargs):  # Logs the message and before executing the decorated function            logger.log(level, log_message)            return func(*args, **kwargs)        @attach_wrapper(wrapper)  # Attaches "set_level" to "wrapper" as attribute        def set_level(new_level):  # Function that allows us to set log level            nonlocal level            level = new_level        @attach_wrapper(wrapper)  # Attaches "set_message" to "wrapper" as attribute        def set_message(new_message):  # Function that allows us to set message            nonlocal log_message            log_message = f"{func.__name__} - {new_message}"        return wrapper    return decorate# Example Usage@log(logging.WARN, "example-param")def somefunc(args):    return argssomefunc("some args")somefunc.set_level(logging.CRITICAL)  # Change log level by accessing internal decorator functionsomefunc.set_message("new-message")  # Change log message by accessing internal decorator functionsomefunc("some args")

2020-05-01 14:42:10,289 - __main__ - WARNING - somefunc - example-param2020-05-01 14:42:10,289 - __main__ - CRITICAL - somefunc - new-message

class Circle:    def __init__(self, x, y, radius):        self.x = x        self.y = y        self.radius = radius    def __repr__(self):        return f"Rectangle({self.x}, {self.y}, {self.radius})"...c = Circle(100, 80, 30)repr(c)# Circle(100, 80, 30)

class MyDict(dict):    def __missing__(self, key):        message = f'{key} not present in the dictionary!'        logging.warning(message)        return message  # Or raise some error instead

# crashing_app.pySOME_VAR = 42class SomeError(Exception):    passdef func():    raise SomeError("Something went wrong...")func()

# Run crashing application~ $ python3 -i crashing_app.pyTraceback (most recent call last):  File "crashing_app.py", line 9, in <module>    func()  File "crashing_app.py", line 7, in func    raise SomeError("Something went wrong...")__main__.SomeError: Something went wrong...>>> # We are interactive shell>>> import pdb>>> pdb.pm()  # start Post-Mortem debugger> .../crashing_app.py(7)func()-> raise SomeError("Something went wrong...")(Pdb) # Now we are in debugger and can poke around and run some commands:(Pdb) p SOME_VAR  # Print value of variable42(Pdb) l  # List surrounding code we are working with  2  3   class SomeError(Exception):  4       pass  5  6   def func():  7  ->     raise SomeError("Something went wrong...")  8  9   func()[EOF](Pdb)  # Continue debugging... set breakpoints, step through the code, etc.

import tracebackimport sysdef func():    try:        raise SomeError("Something went wrong...")    except:        traceback.print_exc(file=sys.stderr)

>>> import func from module>>> func()"This is result..."# Make some changes to "func">>> func()"This is result..."  # Outdated result>>> from importlib import reload; reload(module)  # Reload "module" after changes made to "func">>> func()"New result..."