Try-Except-Else 是 Python 中流量控制的有用工具吗？

Is Using Try-Except-Else in Python Beneficial?

In Python, a common code block encountered is:

try:
   try_this(whatever)
except SomeException as exception:
   #Handle exception
else:
   return something

This pattern raises the question of its purpose.

Reason for Try-Except-Else

Exceptions in Python are frequently utilized for flow control. The Python core developers and the iterator protocol use exceptions for flow control. Try-except-else prevents race conditions that occur in "look-before-you-leap" scenarios.

Exceptions vs. Errors

While exceptions are not errors, Python's cultural norms and libraries differ from other languages. In Python, exceptions are sometimes necessary for control flow. Additionally, using exceptions does not hinder code performance as it does in some compiled languages.

Benefits of Try-Except-Else

Exceptions can:

• Avoid Race Conditions: Ensure up-to-date information and prevent race conditions.
• Pull Error Handling Outside Loops: Optimize interpreted languages that lack automatic loop invariant code motion.
• Simplify Complex Flow Control: Facilitate handling issues far from their origin, such as in hierarchical code structures.

Purpose of Else-Clause

The else-clause in try-except-else allows code to execute without exception handling before the finally-clause. This allows for:

• Executing Unprotected Code: Running code that isn't protected by the try-block, without risking exceptions.
• Differentiating No Exception: Distinguishing code that executes when no exception occurs from code that executes when exceptions are handled.
• Beautification: Aligning exceptional and non-exceptional outcomes for code readability.

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