Sympy常用函数总结

基础

from sympy import *

数学格式输出:

init_printing()

添加变量:

x, y, z, a, b, c = symbols('x y z a b c')

声明分数:

Rational(1, 3)

(displaystyle frac{1}{3})

化简式子:

simplify((x**3 + x**2 - x - 1)/(x**2 + 2*x + 1))

(displaystyle x - 1)

因式分解:

expand((x + 2)*(x - 3))

(displaystyle x^{2} - x - 6)

提取公因式:

factor(x**3 - x**2 + x - 1)

(displaystyle left(x - 1 ight) left(x^{2} + 1 ight))

约分:

cancel((x**2 + 2*x + 1)/(x**2 + x))

(displaystyle frac{x + 1}{x})

裂项:

apart((4*x**3 + 21*x**2 + 10*x + 12)/(x**4 + 5*x**3 + 5*x**2 + 4*x))

(displaystyle frac{2 x - 1}{x^{2} + x + 1} - frac{1}{x + 4} + frac{3}{x})

变换形式:

tan(x).rewrite(sin)

(displaystyle frac{2 sin^{2}{left(x ight)}}{sin{left(2 x ight)}})

数列求和:

Sum(x ** 2, (x, 1, a)).doit()

(displaystyle frac{a^{3}}{3} + frac{a^{2}}{2} + frac{a}{6})

数列求积:

Product(x**2,(x, 1, a)).doit()

(displaystyle a!^{2})

微积分

求导:

diff(cos(x), x)

(displaystyle - sin{left(x ight)})

求高阶导:

diff(x**4, x, 3)

(displaystyle 24 x)

连续求偏导:

diff(exp(x*y*z), x, y, 2, z, 4)

(displaystyle x^{3} y^{2} left(x^{3} y^{3} z^{3} + 14 x^{2} y^{2} z^{2} + 52 x y z + 48 ight) e^{x y z})

不定积分:

integrate(cos(x), x)

(displaystyle sin{left(x ight)})

定积分:

integrate(exp(-x), (x, 0, oo))

(displaystyle 1)

多重积分:

integrate(exp(-x**2 - y**2), (x, -oo, oo), (y, -oo, oo))

(displaystyle pi)

极限:

limit(sin(x)/x, x, 0)

(displaystyle 1)

泰勒展开(到第4阶):

sin(x).series(x, 0, 4)

(displaystyle x - frac{x^{3}}{6} + Oleft(x^{4} ight))

泰勒展开(在x=6处):

exp(x - 6).series(x, 6)

(displaystyle -5 + frac{left(x - 6 ight)^{2}}{2} + frac{left(x - 6 ight)^{3}}{6} + frac{left(x - 6 ight)^{4}}{24} + frac{left(x - 6 ight)^{5}}{120} + x + Oleft(left(x - 6 ight)^{6}; x ightarrow 6 ight))

矩阵

矩阵求逆:

Matrix([[1, 3], [-2, 3]])**-1

(displaystyle left[egin{matrix}frac{1}{3} & - frac{1}{3}\frac{2}{9} & frac{1}{9}end{matrix} ight])

求转置:

Matrix([[1, 2, 3], [4, 5, 6]]).T

(displaystyle left[egin{matrix}1 & 4\2 & 5\3 & 6end{matrix} ight])

生成单位矩阵:

eye(3)

(displaystyle left[egin{matrix}1 & 0 & 0\0 & 1 & 0\0 & 0 & 1end{matrix} ight])

求行列式:

Matrix([[1, 0, 1], [2, -1, 3], [4, 3, 2]]).det()

(displaystyle -1)

化成行阶梯形矩阵:

Matrix([[1, 0, 1, 3], [2, 3, 4, 7], [-1, -3, -3, -4]]).rref()

(displaystyle left( left[egin{matrix}1 & 0 & 1 & 3\0 & 1 & frac{2}{3} & frac{1}{3}\0 & 0 & 0 & 0end{matrix} ight], left( 0, 1 ight) ight))

求列向量空间:

Matrix([[1, 1, 2], [2 ,1 , 3], [3 , 1, 4]]).columnspace()

(displaystyle left[ left[egin{matrix}1\2\3end{matrix} ight], left[egin{matrix}1\1\1end{matrix} ight] ight])

M = Matrix([[3, -2,  4, -2], [5,  3, -3, -2], [5, -2,  2, -2], [5, -2, -3,  3]])

求特征值:

M.eigenvals()

(displaystyle left{ -2 : 1, 3 : 1, 5 : 2 ight})

求特征向量:

M.eigenvects()

(displaystyle left[ left( -2, 1, left[ left[egin{matrix}0\1\1\1end{matrix} ight] ight] ight), left( 3, 1, left[ left[egin{matrix}1\1\1\1end{matrix} ight] ight] ight), left( 5, 2, left[ left[egin{matrix}1\1\1\0end{matrix} ight], left[egin{matrix}0\-1\0\1end{matrix} ight] ight] ight) ight])

求对角化矩阵,返回两个矩阵P、D满足(PDP^{-1}=M)

M.diagonalize()

(displaystyle left( left[egin{matrix}0 & 1 & 1 & 0\1 & 1 & 1 & -1\1 & 1 & 1 & 0\1 & 1 & 0 & 1end{matrix} ight], left[egin{matrix}-2 & 0 & 0 & 0\0 & 3 & 0 & 0\0 & 0 & 5 & 0\0 & 0 & 0 & 5end{matrix} ight] ight))

解方程

求解集:

solveset(x**2 - x, x)

(displaystyle left{0, 1 ight})

求解集(显示多少个重根):

roots(x**3 - 6*x**2 + 9*x, x)

(displaystyle left{ 0 : 1, 3 : 2 ight})

求解集(用Eq构造等式):

solveset(Eq(sin(x), 1), x, domain=S.Reals)

(displaystyle left{2 n pi + frac{pi}{2}; |; n in mathbb{Z} ight})

解线性方程组:

linsolve([x + y + z - 1, x + y + 2*z - 3 ], (x, y, z))

(displaystyle left{left( - y - 1, y, 2 ight) ight})

解线性方程组(矩阵表示):

linsolve(Matrix(([1, 1, 1, 1], [1, 1, 2, 3])), (x, y, z))

(displaystyle left{left( - y - 1, y, 2 ight) ight})

解非线性方程组:

nonlinsolve([exp(x) - sin(y), 1/y - 3], [x, y])

(displaystyle left{left( log{left(sin{left(frac{1}{3} ight)} ight)}, frac{1}{3} ight), left( left{2 n i pi + left(log{left(sin{left(frac{1}{3} ight)} ight)}mod{2 i pi} ight); |; n in mathbb{Z} ight}, frac{1}{3} ight) ight})

解微分方程:

f, g = symbols('f g', cls=Function)
dsolve(Eq(f(x).diff(x, x) - 2*f(x).diff(x) + f(x), sin(x)), f(x))

(displaystyle f{left(x ight)} = left(C_{1} + C_{2} x ight) e^{x} + frac{cos{left(x ight)}}{2})

解不等式组:

from sympy.solvers.inequalities import *
reduce_inequalities([x <= x ** 2], [x])

(displaystyle left(1 leq x wedge x < infty ight) vee left(x leq 0 wedge -infty < x ight))

逻辑代数

from sympy.logic.boolalg import *

合取范式:

to_cnf(~(x | y) | z)

(displaystyle left(z vee eg x ight) wedge left(z vee eg y ight))

析取范式:

to_dnf(x & (y | z))

(displaystyle left(x wedge y ight) vee left(x wedge z ight))

化简逻辑函数:

simplify_logic((~x & ~y & ~z) | ( ~x & ~y & z))

(displaystyle eg x wedge eg y)

from sympy.logic import *

化简最小项之和为析取范式

minterms = [0, 7]
SOPform([x, y, z], minterms)

(displaystyle left(x wedge y wedge z ight) vee left( eg x wedge eg y wedge eg z ight))

化简最小项之和为合取范式

minterms = [[1, 0, 1], [1, 1, 0], [1, 1, 1]]
POSform([x, y, z], minterms)

(displaystyle x wedge left(y vee z ight))

化简最小项之和为析取范式(第7项任取)

minterms = [[1, 0, 1], [1, 1, 0]]
dontcares = [7]
SOPform([x, y, z], minterms, dontcares)

(displaystyle left(x wedge y ight) vee left(x wedge z ight))

数论

from sympy.ntheory import *

阶乘:

factorial(10)

(displaystyle 3628800)

分解质因数:

factorint(300)

(displaystyle left{ 2 : 2, 3 : 1, 5 : 2 ight})

factorint(300, visual=True)

(displaystyle 2^{2} cdot 3^{1} cdot 5^{2})

求欧拉函数:

totient(25)

(displaystyle 20)

判断质数:

isprime(101)
True

莫比乌斯函数:

mobius(13 * 17 * 5)

(displaystyle -1)

乘法逆元(模后者意义):

mod_inverse(3, 5)

(displaystyle 2)

from sympy.ntheory.factor_ import *

求因子:

divisors(36)

(displaystyle left[ 1, 2, 3, 4, 6, 9, 12, 18, 36 ight])

from sympy.ntheory.modular import *

中国剩余定理解同余方程(模数需互质,前三个数为模数,后三个数为余数,返回第一个数为结果):

crt([99, 97, 95], [49, 76, 65])

(displaystyle left( 639985, 912285 ight))

解同余方程(模数不需互质但比中国剩余定理慢,每个元组第一个数为余数,第二个数为模数,返回第一个数为结果):

solve_congruence((2, 3), (3, 5), (2, 7))

(displaystyle left( 23, 105 ight))

from sympy.ntheory.residue_ntheory import *

求原根(如下2在模19意义下的所有幂占满了0到18):

primitive_root(19)

(displaystyle 2)

求离散对数(如下(7^3 mod 15 = 41)):

discrete_log(41, 15, 7)

(displaystyle 3)

原文地址:https://www.cnblogs.com/YuanZiming/p/13070883.html