Table of contents
3. `else` and `finally` blocks
3. The difference between errors and exceptions
When writing code, you often encounter unexpected situations, such as typos, invalid input data, or underlying system problems. These problems often cause the program to error or throw exceptions. Understanding the concepts of errors and exceptions and how to handle them correctly is key to improving the readability and maintainability of your programs.
1. Concept
1. Error
A serious problem occurred during the execution of the program, and the program cannot continue to run. These errors are usually caused by the underlying environment or system, such as operating system errors, hardware failures, etc. Bugs often require fixes or intervention to resolve.
2. Exception:
Exceptions are predictable problems or unusual conditions that arise during program execution. They are often caused by code we write, possibly due to invalid data, faulty logic, or other reasons. Exceptions can be caught and handled in the code to avoid program crashes and take appropriate action to recover, repair or report errors.
2. Exception handling method
1. `try-except` statement
In Python, the code that may cause an exception is wrapped by using the `try-except` language, and then the corresponding processing logic is written in the `except` block. In this way, even if an exception occurs, the program will not terminate execution.
The basic structure of a try-except statement is:
try:
# 可能引发异常的代码块
except ExceptionType:
# 处理特定类型的异常的代码块
else:
# 当没有发生异常时执行的代码块
finally:
# 无论是否发生异常都会执行的最后代码块
In trya code block, we write code that may throw an exception. If an exception occurs, the program will jump to exceptthe code block and execute the corresponding exception handling logic. exceptA specific exception type can be specified later to catch specific types of exceptions, or the exception type can be omitted to catch all exceptions.
elseA block of code is executed when no exception occurs, whereas finallya block of code executes whether or not an exception occurs.
2. Exception type
Python provides a variety of exception types, such as syntax errors, name errors, type errors, etc., and you can choose to catch specific types of exceptions according to specific situations. Additionally, exception classes can be customized to meet specific needs.
3. `else` and `finally` blocks
In addition to `try` and `except` blocks, `else` and `finally` blocks can also be used. The `else` block is executed when no exception occurs, and is used to handle the code logic of normal execution. The code in the `finally` block will be executed regardless of whether an exception occurs, which is often used to ensure cleanup operations such as resource release.
3. The difference between errors and exceptions
The difference between exceptions and errors There are obvious differences between errors, which are mainly reflected in the following aspects:
1. Cause
Bugs are usually serious problems caused by the underlying system or environment, while exceptions are predictable problems caused by the code we write.
2. Processing method
Errors often require repair or intervention for the underlying cause, which cannot be resolved through normal exception handling mechanisms. Exceptions can be caught and processed through the `try-except` statement, so as to maintain the normal execution of the program.
3. Consequences
Errors often prevent a program from continuing or produce erroneous output, which may interrupt the user experience or cause data loss. Reasonable handling of exceptions can avoid program crashes and help to recover, repair or report errors.
4. Matters needing attention
When dealing with errors and exceptions, the following points should be noted:
1. Exceptions should be properly caught and handled to avoid exposing sensitive information and ensure the normal operation of the program.
2. Learn to choose an appropriate exception handling strategy, including catching specific types of exceptions, setting default processing logic, etc.
3. Exception handling should not be too broad or narrow, and unexpected behavior should be avoided according to the specific situation.
4. Error messages and logs to help debug and fix issues, and improve code quality.
Summarize
Errors and exceptions are common problems in the programming process, and it is very important for developers to understand their concepts and handling methods. Errors are serious problems that require low-level intervention to fix; exceptions are predictable problems that can be handled through exception handling mechanisms.
By properly handling exceptions, we can maintain the stability of the program, improve the reliability of the code, and better deal with various abnormal situations in the running of the program.
Whether you are a novice or an experienced developer, when writing Python code, you should pay attention to the importance of error and exception handling, and always remain alert and thinking about the problem and its solution.