How Does Python 3's `round()` Function Differ from Previous Versions, and Why?

Python 3.0 Rounding Behavior

Python 3.0 has introduced significant changes to the round() function's rounding strategy and return type. In Python 2, round(2.5) returned 3, while in Python 3, it returns 2. Similarly, round(3.5) returns 4 in both versions.

This change has been made to adopt the "round half to even" or "banker's rounding" technique. Rounding in Python 3 is now consistent with the IEEE 754 standard for floating-point math, which defines five distinct rounding methods.

Rationale for the Change

The previous rounding behavior ("always round 0.5 up") could result in a slight bias towards larger numbers when performing numerous computations. Python 3's approach eliminates this bias.

Other Programming Languages with Banker's Rounding

Python 3 is not the only programming language that uses banker's rounding. Other mainstream languages such as C , Java, and AppleScript also implement this method.

Implications for Previous Assumptions

The conventional understanding of rounding may not align with the current behavior of round() in Python 3. This can lead to unexpected results when relying on previous assumptions about rounding.

It's important to note that there are other rounding methods in existence, and different programming languages may implement different techniques. When working with floating-point numbers, it's crucial to be aware of the specific rounding algorithm being used to avoid unexpected outcomes.

The above is the detailed content of How Does Python 3's `round()` Function Differ from Previous Versions, and Why?. For more information, please follow other related articles on the PHP Chinese website!