How Does Python 3's `round()` Function Handle Rounding, and Why is it Different from Python 2?

Python 3.x's Rounding Behavior

In Python 3.x, the round() function's rounding strategy has changed significantly compared to Python 2.x. This modification has elicited some confusion and counterintuitive results.

Changed Rounding Strategy

In Python 2.x, halfway cases were rounded away from zero. However, in Python 3.x, these cases are now rounded to the nearest even result. This means that round(2.5) returns 2 instead of 3.

Reasoning Behind the Change

The new rounding strategy, known as "round half to even" or "banker's rounding," is considered the standard rounding method. The previous "always round 0.5 up" technique resulted in a slight bias towards the higher number. This bias could become significant over a large number of calculations.

Other Programming Languages

Python 3.x's rounding behavior is not unique. Several other mainstream programming languages also use banker's rounding, including:

• C#
• Java
• JavaScript
• Perl

However, not all programming languages use banker's rounding by default. Some, such as C , allow developers to specify the rounding method to use.

Banker's Rounding

Banker's rounding is a specific rounding method that rounds ties (e.g., 2.5) to the nearest even result. This method is widely used in finance and statistics because it eliminates the bias towards the higher number.

While Python 3's rounding behavior may initially seem counterintuitive, it is a well-established standard that ensures consistency and accuracy in calculations.

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