CODEWITHSUNDEEP
pythonpython-3.xalgorithmmath
user5609349
user5609349

Reputation:

What is the algorithmic difference between math.ceil() and round() when trailing decimal points are >= 0.5 in Python 3?

What is the algorithmic difference between math.ceil() and round() when trailing decimal points are >= 0.5 in Python 3?

For example,

round(9.5) = 10
round(9.67) = 10
math.ceil(9.5) = 10
math.ceil(9.5) = 10

Upvotes: 4

Views: 785

Answers (1)

Ziyad Edher
Ziyad Edher

Reputation: 2150

From the docs,

[...] if two multiples are equally close, rounding is done toward the even choice (so, for example, both round(0.5) and round(-0.5) are 0, and round(1.5) is 2).

However, math.ceil will always "round" up. I.e. the smallest integer greater than or equal to the input.

Moreover, round and math.ceil differ greatly when executing on negative numbers.

>>> math.ceil(-2.8)
-2
>>> round(-2.8)
-3

Upvotes: 6

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