【转载】python中math模块常用的方法

转自：https://www.cnblogs.com/renpingsheng/p/7171950.html

ceil

#取大于等于x的最小的整数值，如果x是一个整数，则返回x
ceil(x)
Return the ceiling of x as an int.
This is the smallest integral value >= x.

>>> math.ceil(4.01)
5
>>> math.ceil(4.99)
5
>>> math.ceil(-3.99)
-3
>>> math.ceil(-3.01)
-3

copysign

#把y的正负号加到x前面，可以使用0
copysign(x, y)
Return a float with the magnitude (absolute value) of x but the sign
of y. On platforms that support signed zeros, copysign(1.0, -0.0)
returns -1.0.

>>> math.copysign(2,3)
2.0
>>> math.copysign(2,-3)
-2.0
>>> math.copysign(3,8)
3.0
>>> math.copysign(3,-8)
-3.0

cos

#求x的余弦，x必须是弧度
cos(x)
Return the cosine of x (measured in radians).

#math.pi/4表示弧度，转换成角度为45度
>>> math.cos(math.pi/4)
0.7071067811865476
math.pi/3表示弧度，转换成角度为60度
>>> math.cos(math.pi/3)
0.5000000000000001
math.pi/6表示弧度，转换成角度为30度
>>> math.cos(math.pi/6)
0.8660254037844387

degrees

#把x从弧度转换成角度
degrees(x)
Convert angle x from radians to degrees.

>>> math.degrees(math.pi/4)
45.0
>>> math.degrees(math.pi)
180.0
>>> math.degrees(math.pi/6)
29.999999999999996
>>> math.degrees(math.pi/3)
59.99999999999999

e

#表示一个常量

>>> math.e
2.718281828459045

exp

#返回math.e,也就是2.71828的x次方
exp(x)
Return e raised to the power of x.

>>> math.exp(1)
2.718281828459045
>>> math.exp(2)
7.38905609893065
>>> math.exp(3)
20.085536923187668

expm1

#返回math.e的x(其值为2.71828)次方的值减１
expm1(x)
Return exp(x)-1.
This function avoids the loss of precision involved in the direct evaluation of exp(x)-1 for small x.

>>> math.expm1(1)
1.718281828459045
>>> math.expm1(2)
6.38905609893065
>>> math.expm1(3)
19.085536923187668

fabs

#返回x的绝对值
fabs(x)
Return the absolute value of the float x.

>>> math.fabs(-0.003)
0.003
>>> math.fabs(-110)
110.0
>>> math.fabs(100)
100.0

factorial

#取x的阶乘的值
factorial(x) -> Integral
Find x!. Raise a ValueError if x is negative or non-integral.

>>> math.factorial(1)
1
>>> math.factorial(2)
2
>>> math.factorial(3)
6
>>> math.factorial(5)
120
>>> math.factorial(10)
3628800

floor

#取小于等于x的最大的整数值，如果x是一个整数，则返回自身
floor(x)
Return the floor of x as an int.
This is the largest integral value <= x.

>>> math.floor(4.1)
4
>>> math.floor(4.999)
4
>>> math.floor(-4.999)
-5
>>> math.floor(-4.01)
-5

fmod

#得到x/y的余数，其值是一个浮点数
fmod(x, y)
Return fmod(x, y), according to platform C.  x % y may differ.

>>> math.fmod(20,3)
2.0
>>> math.fmod(20,7)
6.0

frexp

#返回一个元组(m,e),其计算方式为：x分别除0.5和1,得到一个值的范围，
#2**e的值在这个范围内，e取符合要求的最大整数值,然后x/(2**e),得到m的值
#如果x等于0,则m和e的值都为0,m的绝对值的范围为(0.5,1)之间，不包括0.5和1
frexp(x)
Return the mantissa and exponent of x, as pair (m, e).
m is a float and e is an int, such that x = m * 2.**e.
If x is 0, m and e are both 0.  Else 0.5 <= abs(m) < 1.0.

>>> math.frexp(10)
(0.625, 4)
>>> math.frexp(75)
(0.5859375, 7)
>>> math.frexp(-40)
(-0.625, 6)
>>> math.frexp(-100)
(-0.78125, 7)
>>> math.frexp(100)
(0.78125, 7)

fsum

#对迭代器里的每个元素进行求和操作
fsum(iterable)
Return an accurate floating point sum of values in the iterable.
Assumes IEEE-754 floating point arithmetic.

>>> math.fsum([1,2,3,4])
10.0
>>> math.fsum((1,2,3,4))
10.0
>>> math.fsum((-1,-2,-3,-4))
-10.0
>>> math.fsum([-1,-2,-3,-4])
-10.0

gcd

#返回x和y的最大公约数
gcd(x, y) -> int
greatest common divisor of x and y

>>> math.gcd(8,6)
2
>>> math.gcd(40,20)
20
>>> math.gcd(8,12)
4

hypot

#得到(x**2+y**2),平方的值
hypot(x, y)
Return the Euclidean distance, sqrt(x*x + y*y).

>>> math.hypot(3,4)
5.0
>>> math.hypot(6,8)
10.0

isfinite

#如果x是不是无穷大的数字,则返回True,否则返回False
isfinite(x) -> bool
Return True if x is neither an infinity nor a NaN, and False otherwise.

>>> math.isfinite(100)
True
>>> math.isfinite(0)
True
>>> math.isfinite(0.1)
True
>>> math.isfinite("a")
>>> math.isfinite(0.0001)
True

isinf

#如果x是正无穷大或负无穷大，则返回True,否则返回False
isinf(x) -> bool
Return True if x is a positive or negative infinity, and False otherwise.

>>> math.isinf(234)
False
>>> math.isinf(0.1)
False

isnan

#如果x不是数字True,否则返回False
isnan(x) -> bool
Return True if x is a NaN (not a number), and False otherwise.

>>> math.isnan(23)
False
>>> math.isnan(0.01)
False

ldexp

#返回x*(2**i)的值
ldexp(x, i)
Return x * (2**i).

>>> math.ldexp(5,5)
160.0
>>> math.ldexp(3,5)
96.0

log

#返回x的自然对数，默认以e为基数，base参数给定时，将x的对数返回给定的base,计算式为：log(x)/log(base)
log(x[, base])
Return the logarithm of x to the given base.
If the base not specified, returns the natural logarithm (base e) of x.

>>> math.log(10)
2.302585092994046
>>> math.log(11)
2.3978952727983707
>>> math.log(20)
2.995732273553991

log10

#返回x的以10为底的对数
log10(x)
Return the base 10 logarithm of x.

>>> math.log10(10)
1.0
>>> math.log10(100)
2.0
#即10的1.3次方的结果为20
>>> math.log10(20)
1.3010299956639813

log1p

#返回x+1的自然对数(基数为e)的值
log1p(x)
Return the natural logarithm of 1+x (base e).
The result is computed in a way which is accurate for x near zero.

>>> math.log(10)
2.302585092994046
>>> math.log1p(10)
2.3978952727983707
>>> math.log(11)
2.3978952727983707

log2

#返回x的基2对数
log2(x)
Return the base 2 logarithm of x.

>>> math.log2(32)
5.0
>>> math.log2(20)
4.321928094887363
>>> math.log2(16)
4.0

modf

#返回由x的小数部分和整数部分组成的元组
modf(x)
Return the fractional and integer parts of x.  Both results carry the sign
of x and are floats.

>>> math.modf(math.pi)
(0.14159265358979312, 3.0)
>>> math.modf(12.34)
(0.33999999999999986, 12.0)

pi

#数字常量，圆周率

>>> print(math.pi)
3.141592653589793

pow

#返回x的y次方，即x**y
pow(x, y)
Return x**y (x to the power of y).

>>> math.pow(3,4)
81.0
>>>
>>> math.pow(2,7)
128.0

radians

#把角度x转换成弧度
radians(x)
Convert angle x from degrees to radians.

>>> math.radians(45)
0.7853981633974483
>>> math.radians(60)
1.0471975511965976

sin

#求x(x为弧度)的正弦值
sin(x)
Return the sine of x (measured in radians).

>>> math.sin(math.pi/4)
0.7071067811865475
>>> math.sin(math.pi/2)
1.0
>>> math.sin(math.pi/3)
0.8660254037844386

sqrt

#求x的平方根
sqrt(x)
Return the square root of x.

>>> math.sqrt(100)
10.0
>>> math.sqrt(16)
4.0
>>> math.sqrt(20)
4.47213595499958

tan

#返回x(x为弧度)的正切值
tan(x)
Return the tangent of x (measured in radians).

>>> math.tan(math.pi/4)
0.9999999999999999
>>> math.tan(math.pi/6)
0.5773502691896257
>>> math.tan(math.pi/3)
1.7320508075688767

trunc

#返回x的整数部分
trunc(x:Real) -> Integral
Truncates x to the nearest Integral toward 0. Uses the __trunc__ magic method.

>>> math.trunc(6.789)
6
>>> math.trunc(math.pi)
3
>>> math.trunc(2.567)
2