python数学模块(math/decimal模块)

# -*- coding: utf-8 -*-
import math

# math库常用变量
print("math.pi = ", math.pi)
print('math.e = ', math.e)
print('math.inf = ', math.inf)
print('math.nan = ', math.nan)


# math库常用函数

print('math.ceil()向上取整，math.ceil(2.3) = ', math.ceil(2.3))
print('math.ceil()向上取整，math.ceil(2.5) = ', math.ceil(2.5))
print('math.ceil()向上取整，math.ceil(2.0) = ', math.ceil(2.0))
print('math.ceil()向上取整，math.ceil(2.8) = ', math.ceil(2.8))
print('math.ceil()向上取整，math.ceil(-2.8) = ', math.ceil(-2.8))

print('math.floor()向下取整，math.floor(2.3) = ', math.floor(2.3))
print('math.floor()向下取整，math.floor(2.5) = ', math.floor(2.5))
print('math.floor()向下取整，math.floor(2.0) = ', math.floor(2.0))
print('math.floor()向下取整，math.floor(2.8) = ', math.floor(2.8))
print('math.floor()向下取整，math.floor(-2.8) = ', math.floor(-2.8))

print('round()四舍五入，round(2.3) = ', round(2.3))
print('round()四舍五入，roundr(2.5) = ', round(2.5))
print('round()四舍五入，round(2.0) = ', round(2.0))
print('round()四舍五入，round(2.8) = ', round(2.8))
print('round()四舍五入，round(-2.8) = ', round(-2.8))

print('math.fabs()获取绝对值，math.fabs(2.3) = ', math.fabs(2.3))
print('math.fabs()获取绝对值，math.fabs(-2.3) = ', math.fabs(-2.3))
print('math.fabs()获取绝对值，math.fabs(-2.0) = ', math.fabs(-2.0))
print('math.fabs()获取绝对值，math.fabs(-2) = ', math.fabs(-2))

print('abs()获取绝对值，abs(2.3) = ', abs(2.3))
print('abs()获取绝对值，abs(-2.3) = ', abs(-2.3))
print('abs()获取绝对值，abs(-2.0) = ', abs(-2.0))
print('abs()获取绝对值，abs(-2) = ', abs(-2))

print('math.fmod(x,y)获取x/y的余数，math.fmod(2,3) = ' ,math.fmod(2,3))
print('math.pow(x,y)获取x的n次方,math.pow(2,3) = ', math.pow(2,3))
print('math.sqrt()获取开放根,math.sqrt(4) = ', math.sqrt(4))
print('fsum()获取序列中所有元素的和，fsum([1,2,3,4,5,6]) = ', math.fsum([1,2,3,4,5,6]))
print('sum()获取序列中所有元素的和，sum([1,2,3,4,5,6]) = ', sum([1,2,3,4,5,6]))
print('math.modf()获取浮点数的小数和整数部分，math.modf(2.3) = ', math.modf(2.3))
print('math.trunc()获取浮点数的整数部分，math.trunc(2.3) = ', math.trunc(2.3))
print('math.copysign(n1,n2)把第二个数的正负号赋值给第一个浮点数，math.copysign(-2.3,1) = ', math.copysign(-2.3,1))
print('math.copysign(n1,n2)把第二个数的正负号赋值给第一个浮点数，math.copysign(2.3,-1) = ', math.copysign(2.3,-1))
print('math.gcd(x,y)获取x和y的最大公约数，math.gcd(16,24) = ', math.gcd(16,24))
try:
    print('math.factorial()获取阶乘，math.factorial(3) = ', math.factorial(3))
    print('math.factorial()获取阶乘，math.factorial(2.3) = ', math.factorial(2.3))
    print('math.factorial()获取阶乘，math.factorial(-2) = ', math.factorial(-2))
except ValueError as e:
    print(e)
finally:
    pass

# -*- coding: utf-8 -*-
import decimal

"""
decimal.getcontext().prec = 3  # 设置有效数字是3位
print(decimal.Decimal(2.32) + decimal.Decimal(3.01))

decimal.getcontext().prec = 2  # 设置有效数字是2位
print(decimal.Decimal(2.32) + decimal.Decimal(3.01))
"""

# quantize()设置小数位数
num = decimal.Decimal(1.23456789).quantize(decimal.Decimal('0.000'))
print(num)