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Python Exception Handling: Built-In Exceptions & Best Practices

Exception handling is an essential aspect of programming in Python. It is a mechanism that allows you to handle and recover from unexpected errors and exceptions that may occur during the execution of a program. Python provides a robust and easy-to-use exception handling mechanism that helps developers to build more reliable and stable applications.

An exception is an error that occurs during the execution of a program. It is a signal that something has gone wrong, and the program cannot proceed with its normal operation. For example, if you try to divide a number by zero or access an index that does not exist in a list, you will get an exception.

Python provides a wide range of built-in exceptions that cover different types of errors.

  • NameError – raised when an undefined variable is used.

  • TypeError – raised when an operation or function is applied to an object of an inappropriate type.

  • ValueError – raised when a function receives an argument of the correct type, but with an inappropriate value.

  • ZeroDivisionError – raised when you try to divide a number by zero.

  • IndexError – raised when you try to access an index that does not exist in a list or tuple.

  • KeyError – raised when you try to access a non-existent key in a dictionary.

  • FileNotFoundError – raised when a file or directory is not found.

  • MemoryError – raised when the interpreter runs out of memory.

  • SyntaxError – raised when there is a syntax error in the code.

  • ModuleNotFoundError – raised when an import statement fails to find the specified module.

Python provides a try-except statements for handling exceptions. The try block contains the code that may raise an exception, and the except block contains the code that handles the exception.

Best Practices

Here are some best practices for writing exception handling code in Python:

  • It's good practice to catch only the specific exceptions that you expect to occur. Catching all exceptions using a bare except block can mask bugs and make it harder to diagnose and fix problems.

  • Exceptions should be handled at the appropriate level of your program. For example, if an exception occurs in a function, handle it in that function rather than letting it propagate up the call stack.

  • Exception handling code should be simple and concise. Avoid putting too much logic in your exception handling code.

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