sympy

Prevent Sympy from rearranging the equation

由 自闭症网瘾萝莉.ら 提交于 2019-11-27 16:05:12
Perhaps im overlooking the obvious but how do you prevent sympy from rearranging equations? Im using Sympy in the iPython notebook so i can easily copy-paste the Latex code to Lyx, but i want the equations in the same order as i defined them. For example, the formula for grey-body radiation as a function of its temperature: Sympy automatically places the Temperature component to the front, which gives a very unusual representation of the formula. Is there anyway to prevent this? Currently, there is no way in SymPy to print things exactly as they are entered, because that information isn't even

What causes this error (AttributeError: 'Mul' object has no attribute 'cos') in Python?

由 寵の児 提交于 2019-11-27 15:50:47
I am getting the following error code when trying to evaluate a definite integral in Python. AttributeError Traceback (most recent call last) <ipython-input-7-2be8718c68ec> in <module>() 7 x, n = symbols('x n') 8 ----> 9 f = (cos(n*x))*(x**2-pi**2)^2 10 integrate(f,(x,-n*pi,n*pi)) 11 AttributeError: 'Mul' object has no attribute 'cos' I have copied my input code below. Thanks for any help. from pylab import * from sympy import * from numpy import * init_printing(use_unicode=False, wrap_line=False, no_global=True) x, n = symbols('x n') f = (cos(n*x))*(x**2-pi**2)^2 integrate(f,(x,-n*pi,n*pi))

SymPy - Arbitrary number of Symbols

由 狂风中的少年 提交于 2019-11-27 13:09:13
问题 I am coding a function that solves an arbitrary number of simultaneous equations. The number of equations is set by one of the parameters of the function and each equation is built from a number of symbols - as many symbols as there are equations. This means that I can't simply hardcode the equations, or even the symbols needed to put together the equations; the function needs to be able to handle any number of equations. So, my question is, how do I produce a list of symbols? I have one

How to extract all coefficients in sympy

由 跟風遠走 提交于 2019-11-27 11:21:27
问题 You can get a coefficient of a specific term by using coeff(); x, a = symbols("x, a") expr = 3 + x + x**2 + a*x*2 expr.coeff(x) # 2*a + 1 Here I want to extract all the coefficients of x, x**2 (and so on), like; # for example expr.coefficients(x) # want {1: 3, x: (2*a + 1), x**2: 1} There is a method as_coefficients_dict(), but it seems this doesn't work in the way I want; expr.as_coefficients_dict() # {1: 3, x: 1, x**2: 1, a*x: 2} expr.collect(x).as_coefficients_dict() # {1: 3, x**2: 1, x*(2

sympy: trigonometric sum-product identities

由 我只是一个虾纸丫 提交于 2019-11-27 06:11:40
问题 I have an expression: sin(x)+sin(y) There is a well-known trig identity to express this as the product of sin and cos. Is there a way to get sympy to apply this identity? simplify and trigsimp do nothing. 回答1: trigsimp , as Aristocrates points out, does the reverse, because sin(x) + sin(y) is simpler than 2*sin((x + y)/2)*cos((x - y)/2) . trigsimp internally uses an algorithm based on a paper by Fu, et. al., which does pattern matching on various trigonometric identities. If you look at the

Evaluating a mathematical expression (function) for a large number of input values fast

由 僤鯓⒐⒋嵵緔 提交于 2019-11-27 02:49:21
问题 The following questions Evaluating a mathematical expression in a string Equation parsing in Python Safe way to parse user-supplied mathematical formula in Python Evaluate math equations from unsafe user input in Python and their respective answers made me think how I could parse a single mathematical expression (in general terms along the lines of this answer https://stackoverflow.com/a/594294/1672565) given by a (more or less trusted) user efficiently for 20k to 30k input values coming from

How to calculate expression using sympy in python

由 青春壹個敷衍的年華 提交于 2019-11-27 01:36:27
问题 I need a calculate below expression using sympy in python? exp = '(a+b)*40-(c-a)/0.5' In a=6 , b=5 , c=2 this case how to calculate expression using sympy in python? Please help me. 回答1: The documentation is here: http://docs.sympy.org/. You should really read it! To "calculate" your expression, write something like this: from sympy import Symbol a = Symbol("a") b = Symbol("b") c = Symbol("c") exp = (a+b)*40-(c-a)/0.5 And that's it. If you meant something else by "calculate", you could also

Prevent Sympy from rearranging the equation

由 假如想象 提交于 2019-11-26 18:34:33
问题 Perhaps im overlooking the obvious but how do you prevent sympy from rearranging equations? Im using Sympy in the iPython notebook so i can easily copy-paste the Latex code to Lyx, but i want the equations in the same order as i defined them. For example, the formula for grey-body radiation as a function of its temperature: Sympy automatically places the Temperature component to the front, which gives a very unusual representation of the formula. Is there anyway to prevent this? 回答1:

What causes this error (AttributeError: 'Mul' object has no attribute 'cos') in Python?

由 六眼飞鱼酱① 提交于 2019-11-26 17:19:32
问题 I am getting the following error code when trying to evaluate a definite integral in Python. AttributeError Traceback (most recent call last) <ipython-input-7-2be8718c68ec> in <module>() 7 x, n = symbols('x n') 8 ----> 9 f = (cos(n*x))*(x**2-pi**2)^2 10 integrate(f,(x,-n*pi,n*pi)) 11 AttributeError: 'Mul' object has no attribute 'cos' I have copied my input code below. Thanks for any help. from pylab import * from sympy import * from numpy import * init_printing(use_unicode=False, wrap_line

How to solve a pair of nonlinear equations using Python?

由 末鹿安然 提交于 2019-11-26 14:22:18
What's the (best) way to solve a pair of non linear equations using Python. (Numpy, Scipy or Sympy) eg: x+y^2 = 4 e^x+ xy = 3 A code snippet which solves the above pair will be great for numerical solution, you can use fsolve: http://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.fsolve.html#scipy.optimize.fsolve from scipy.optimize import fsolve import math def equations(p): x, y = p return (x+y**2-4, math.exp(x) + x*y - 3) x, y = fsolve(equations, (1, 1)) print equations((x, y)) Krastanov If you prefer sympy you can use nsolve . >>> nsolve([x+y**2-4, exp(x)+x*y-3], [x, y], [1, 1
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