1.9//2  #向下取整
0.0
1.9/2   #不取整
0.95

import math
math.floor(1/2)  #向下取整
0
math.ceil(1/2)   #向上取整
round(0.3)       #四舍五入
0
round(0.8)       #四舍五入
1

round(1.22222,2)   #保留2位小數(shù)
1.22

            
          

“”"
從數(shù)學(xué)理論上來說，四舍五入，round(10.5,0)應(yīng)該進(jìn)位為11,
但是到了python3.5的doc中，文檔變成了"values are rounded to the closest multiple of 10 to the power minus ndigits; if two multiples are equally close, rounding is done toward the even choice." 如果距離兩邊一樣遠(yuǎn)，會保留到偶數(shù)的一邊。比如round(0.5)和round(-0.5)都會保留到0，而round(1.5)會保留到2。
“”"

            
              round(10.500000001,0)
11.0

round(10.5,0)
10.0

            
          

計(jì)算結(jié)果精度與預(yù)期不符的解決方法：

            
              >>> 10-9.9
0.09999999999999964
>>> (10*100-9.9*100)/100
0.1