Python中「assert」的本質是什麼？

What is the Essence of "assert" in Python?

The "assert" statement in Python serves a dual purpose:

• Debugging Assistant: It promptly detects issues with clear causes early in code execution, preventing their proliferation through subsequent layers. For instance, it can expose type errors that might otherwise manifest as cryptic exceptions later on.
• Documentation Annotation: Assertions act as explicit guarantees that a particular condition holds true at a specific point in the code. This aids fellow developers in understanding the expected state and behavior of the application.

Assert in Action

When encountered, the statement:

assert condition

informs the program to evaluate the supplied condition. If false, an error is instantly raised.

In Python, this function resembles:

if not condition:
    raise AssertionError()

To illustrate, consider the following interaction in the Python shell:

>>> assert True # Nothing happens
>>> assert False
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError

Message and Disablement

Assertions can accommodate an auxiliary message, easing error analysis. Additionally, they can be disabled when executing code in optimized mode, where debug evaluates to false:

assert False, "Oh no! This assertion failed!"

Grammatical Considerations

Remember that "assert" is a statement, not a function. Therefore, it should not be invoked with parentheses like so:

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