Python变量如何以标准化方式交换值？

Can Python Variables Swap Their Values in a Standardized Way?

Python's versatile syntax allows for various methods to swap variable values. However, is there a commonly accepted standard?

The "Simultaneous Assignment" Method

One prevalent approach is the simultaneous assignment syntax, where two variables swap their values in a single line:

left, right = right, left

This works because Python evaluates expressions left to right and performs assignments from right to left. The右端表达式("右, 左")首先被评估，创建一个包含两个元素的元组。然后，该元组被拆包并分配给左端变量。

Exploring the Working Mechanism

Diving deeper into the evaluation process:

1. The tuple is created in memory, containing the objects referenced by "right" and "left" at the time of execution.
2. The left-hand side (lhs) is then evaluated, assigning the tuple to it.
3. The lhs is unpacked, assigning the first element of the tuple to "left" (formerly containing "right") and the second element to "right" (formerly containing "left").

Standard or Convention?

This simultaneous assignment method has become the "standard" due to its conciseness and clarity. While there are no explicit rules in Python, community usage and documentation establish this syntax as the preferred approach for variable swapping.

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