python: round 内建函数 (四舍五入)

Syntax

round(number[, ndigits=0])

对 number 进行 四舍五入：

Args :

• number ：可正可负 。
• ngigits ：保留 ngigits 位 小数 。

Test

assert round(0.5) == 1.0assert round(-0.5) == -1.0assert round(12345.678, -5) == 0.0assert round(12345.678, -4) == 10000.0assert round(12345.678, -3) == 12000.0assert round(12345.678, -2) == 12300.0assert round(12345.678, -1) == 12350.0assert round(12345.678, 0) == 12346.0 == round(12345.678)assert round(12345.678, 1) == 12345.7assert round(12345.678, 2) == 12345.68assert round(12345.678, 3) == 12345.678assert round(12345.678, 4) == 12345.6780

round 陷阱

举例

print round(1.045, 2)print round(1.055, 2)

打印结果：

1.041.05

原因

见 Python 为什么不解决四舍五入(round)的“bug”？ 。

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