python 地板除法(floor)和截断除法(trunc)

math.floor() & math.trunc()

math.floor 和 math.trunc的官方不同版本的介绍如下：

math.floor:
python2.7:  Return the floor of x as a float, the largest integer value less than or equal to x.
python3.5:  Return the floor of x, the largest integer less than or equal to x. If x is not a float, delegates to x.__floor__(), which should return an Integral value.

math.trunc:
python2.7:  Return the Real value x truncated to an Integral (usually a long integer). Uses the __trunc__ method.
python3.5:  Return the Real value x truncated to an Integral (usually an integer). Delegates to x.__trunc__().

math.ceil:
python2.7:  Return the ceiling of x as a float, the smallest integer value greater than or equal to x.
python3.5:  Return the ceiling of x, the smallest integer greater than or equal to x. If x is not a float, delegates to x.__ceil__(), which should return an Integral value.

root@pts/4 $ cat python_math_floor_and_trunc.py
#!/usr/bin/env pyton
#-*- codingL utf-8 -*-

import math

a = 3
b = 3.12
c = 3.67

print('-'*20+'a = 3; b = 3.12; c = 3.67'+'-'*20)
print('-'*20+'math.ceil a b c'+'-'*20)
print(math.ceil(a))
print(math.ceil(b))
print(math.ceil(c))

print('-'*20+'math.floor a b c'+'-'*20)
print(math.floor(a))
print(math.floor(b))
print(math.floor(c))

print('-'*20+'math.trunc a b c'+'-'*20)
print(math.trunc(a))
print(math.trunc(b))
print(math.trunc(c))

root@pts/4 $ python python_math_floor_and_trunc.py
--------------------a = 3; b = 3.12; c = 3.67--------------------
--------------------math.ceil a b c--------------------
3.0
4.0
4.0
--------------------math.floor a b c--------------------
3.0
3.0
3.0
--------------------math.trunc a b c--------------------
3
3
3

root@pts/5 $ python python_math_floor_and_trunc.py
--------------------a = 3; b = 3.12; c = 3.67--------------------
--------------------math.ceil a b c--------------------
3
4
4
--------------------math.floor a b c--------------------
3
3
3
--------------------math.trunc a b c--------------------
3
3
3

总结来说：
math.trunc 不管是在Python2.7或者是Python3.5版本中最终的结果都是`截断`之后的`整数`

math.ceil/math.floor 在Python2.7版本返回值是`浮点数`；在python3.5版本是`整数`
math.ceil 是返回 大于或者等于当前值的`最小整数`
math.floor 是返回 小于或者等于当前值的`最大整数`