Python 中的错误处理和日志记录

try:

    # code that might raise an exception

    pass

except exceptiontype as e:

    # code to handle the exception

    pass

# handling division by zero

try:

    result = 10 / 0

except zerodivisionerror:

    print("error: cannot divide by zero.")

# the code will continue its execution

try:

    # code that might raise an exception

    pass

except exceptiontype as e:

    # code to handle the exception

    pass

else:

    # code to run if no exception is raised

    pass

finally:

    # code that always runs, regardless of whether an exception was raised or not

    pass

try:

    # open the file

    file = open('example.txt', 'r')

    # read from the file

    content = file.read()

    # print file content (this will only execute if no exceptions are raised)

    print(content)

except filenotfounderror as e:

    # handle the specific exception

    print(f"error: {e}")

except exception as e:

    # handle any other exceptions

    print(f"an unexpected error occurred: {e}")

else:

    # code that runs if no exception was raised in the try block

    print("file read successfully.")

finally:

    # ensure the file is closed, regardless of whether an exception was raised

    try:

        file.close()

        print("file closed.")

    except:

        # handle the case Where file was never opened (e.g., if open() failed)

        print("file was not opened or already closed.")

filename = 'non_existent_file.txt'

if filename:  # this only checks if filename is not empty, not if the file exists

    # the following line will raise an exception if the file doesn't exist

    content = open(filename, 'r').read()  # this will crash if the file does not exist

    if content:

        print("file content exists:")

        print(content)

    else:

        print("file is empty.")

else:

    print("filename is invalid.")

filename = 'non_existent_file.txt'

try:

    content = open(filename, 'r').read()

    if content:

        print("file content exists:")

        print(content)

    else:

        print("file is empty.")

except filenotfounderror:

    print("error: file not found.")

# define a custom exception

class walletbalanceerror(exception):

    def __init__(self, message):

        self.message = message

        super().__init__(self.message)

# function that checks wallet balance

def check_wallet_balance(wallet_balance, required_balance):

    if wallet_balance

<p>在这个例子中，我们定义了一个自定义异常 walletbalanceerror 来处理钱包余额不符合要求的情况。如果钱包余额不足，check_wallet_balance 函数会引发此异常，并提供清晰具体的错误消息。</p>

<p>python 中的自定义异常通过明确定义特定的错误条件并以结构化方式处理它们，帮助使代码更具可读性和可维护性。</p>

<p>现在我们知道了如何处理 python 中的错误，是时候了解发生这些错误时该怎么办了。有很多策略，但记录这些错误可以帮助以后发现问题并纠正它们。在本文的下一部分中，我们将探讨日志记录。</p>

<h2>

  使用 python 进行日志记录

</h2>

<p>日志记录可帮助开发人员跟踪应用程序或程序中的错误、事件或任何运行时信息。日志记录是软件工程的一个重要且关键的方面，因为它能够记录开发后应用程序中所有正确或错误的情况。日志记录是监控最重要的支柱之一。</p>

<p>python 提供了一个内置模块，可用于日志记录</p>

<p>目的。要使用这个模块，首先要做的就是导入它。<br></p>

<pre class="brush:php;toolbar:false">import logging

import logging

# set up the basic configuration for logging

logging.basicconfig(filename='app.log', level=logging.debug,

                    fORMat='%(asctime)s - %(name)s - %(levelname)s - %(message)s')

# log messages of various severity levels

logging.debug('this is a debug message')

logging.info('this is an info message')

logging.warning('this is a warning message')

logging.error('this is an error message')

logging.critical('this is a critical message')

import logging

# create a custom logger

logger = logging.getlogger('my_custom_logger')

# set the log level for the custom logger

logger.setlevel(logging.debug)

# create a file handler to write logs to a file

file_handler = logging.filehandler('custom.log')

# create a console handler to output logs to the console

console_handler = logging.streamhandler()

# set log levels for the handlers

file_handler.setlevel(logging.error)

console_handler.setlevel(logging.debug)

# create a formatter for log messages

formatter = logging.formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')

# add the formatter to the handlers

file_handler.setformatter(formatter)

console_handler.setformatter(formatter)

# add the handlers to the logger

logger.addhandler(file_handler)

logger.addhandler(console_handler)

# log messages using the custom logger

logger.debug('this is a debug message')

logger.info('this is an info message')

logger.warning('this is a warning message')

logger.error('this is an error message')

logger.critical('this is a critical message')

from flask import Flask, request

import logging

app = Flask(__name__)

# Set up the basic configuration for logging

logging.basicConfig(filename='webapp.log', level=logging.INFO,

                    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s')

@app.route('/')

def index():

    app.logger.info('Index page accessed')

    return 'Welcome to the Flask Web Application!'

@app.route('/error')

def error():

    app.logger.error('Error page accessed')

    raise ValueError('This is a simulated error')

if __name__ == '__main__':

    app.run(debug=True)