Questions tagged [sympy]
SymPy is an open source Python library for symbolic mathematics.
sympy
5,805
questions
93
votes
9
answers
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How to solve a pair of nonlinear equations using Python?
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
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62
votes
5
answers
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How to extract all coefficients in sympy
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 ...
- 2,160
61
votes
4
answers
59k
views
How to pretty print in ipython notebook via sympy?
I tried pprint, print, the former only prints Unicode version, and the latter doesn't do pretty prints.
from sympy import symbols, Function
import sympy.functions as sym
from sympy import ...
- 21.4k
60
votes
3
answers
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views
How can I get a list of the symbols in a sympy expression?
For example, if I run
import sympy
x, y, z = sympy.symbols('x:z')
f = sympy.exp(x + y) - sympy.sqrt(z)
is there any method of f that I can use to get a list or tuple of sympy.Symbol objects that the ...
- 4,501
55
votes
1
answer
22k
views
What is the difference between SymPy and Sage?
What is the difference between SymPy and Sage a.k.a. SageMath?
- 1,011
51
votes
6
answers
68k
views
How can I solve system of linear equations in SymPy?
Sorry, I am pretty new to sympy and python in general.
I want to solve the following underdetermined linear system of equations:
x + y + z = 1
x + y + 2z = 3
- 657
44
votes
5
answers
48k
views
What is the best way to convert a SymPy matrix to a numpy array/matrix
I am not sure if the approach I've been using in sympy to convert a MutableDenseMatrix to a numpy.array or numpy.matrix is a good current practice.
I have a symbolic matrix like:
g = sympy.Matrix( [[...
- 57.9k
43
votes
6
answers
48k
views
How to define a mathematical function in SymPy?
I've been trying this now for hours. I think I don't understand a basic concept, that's why I couldn't answer this question to myself so far.
What I'm trying is to implement a simple mathematical ...
- 8,248
42
votes
4
answers
25k
views
Evaluate sympy expression from an array of values
I'm experimenting with sympy and I've hit upon an issue I can't work out.
Using scipy I can write an expression and evaluate it for an array of x values as follows:
import scipy
xvals = scipy.arange(...
- 423
40
votes
6
answers
47k
views
Is it possible to plot implicit equations?
I would like to plot implicit equations (of the form f(x, y)=g(x, y) eg. X^y=y^x) in Matplotlib. Is this possible?
- 1,209
38
votes
7
answers
24k
views
Get a value from solution set returned as finiteset by Sympy
I`m creating a script in Python Sympy library and trying to access the result returned by solveset() and linsolve() functions. My problem is that the object returned by these functions is of type ...
37
votes
5
answers
19k
views
Sympy - Comparing expressions
Is there a way to check if two expressions are mathematically equal? I expected
tg(x)cos(x) == sin(x) to output True, but it outputs False. Is there a way to make such comparisons with sympy? Another ...
- 721
35
votes
3
answers
63k
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How to substitute multiple symbols in an expression in sympy?
Assigning a variable directly does not modify expressions that used the variable retroactively.
>>> from sympy import Symbol
>>> x = Symbol('x')
>>> y = Symbol('y')
>>...
- 1,442
33
votes
8
answers
183k
views
plus/minus operator for python ±
I am looking for a way to do a plus/minus operation in python 2 or 3. I do not know the command or operator, and I cannot find a command or operator to do this.
Am I missing something?
- 808
33
votes
7
answers
18k
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SymPy - Arbitrary number of Symbols
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 ...
- 5,002
33
votes
4
answers
15k
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how to handle an asymptote/discontinuity
When plotting a graph with a discontinuity/asymptote/singularity/whatever, is there any automatic way to prevent Matplotlib from 'joining the dots' across the 'break'? (please see code/image below).
I ...
- 1,209
28
votes
3
answers
11k
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Is there any way to get the step-by-step solution in SymPy?
Is there any way to get the step-by-step solution in SymPy? For example:
x**2-5 = 4
step 1 x**2-5+5=4+5
step 2 : x**2=9
step 3 :x = 3 or x= -3
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25
votes
5
answers
30k
views
How to calculate expression using sympy in python
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.
- 6,523
25
votes
2
answers
95k
views
Any way to solve a system of coupled differential equations in python?
I've been working with sympy and scipy, but can't find or figure out how to solve a system of coupled differential equations (non-linear, first-order).
So is there any way to solve coupled ...
- 760
23
votes
3
answers
32k
views
Inverse of a matrix in SymPy?
I was wondering how to create a matrix and compute its inverse using SymPy in Python?
For example, for this symbolic matrix:
- 96.9k
23
votes
3
answers
16k
views
How to check the current version of sympy and upgrade to the latest version?
How to check the current version of SymPy and upgrade to the latest version?
I am using macOS. The way I installed my current version is using pip install sympy.
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22
votes
3
answers
17k
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Convert a LaTex formula to a type that can be used inside SymPy
I want to parse LaTeX formulas and directly use them as SymPy expressions. In other words, what I need is something similar to sympify:
from sympy import sympify
f = sympify('x^2 + sin(y) + 1/2')
...
- 245
20
votes
2
answers
34k
views
Using Sympy Equations for Plotting
What is the best way to create a Sympy equation, do something like take the derivative, and then plot the results of that equation?
I have my symbolic equation, but can't figure out how to make an ...
- 1,016
20
votes
4
answers
17k
views
SymPy: Limit symbol/variable to interval
Using SymPy, is it possible to limit the possible values of a symbol/variable to a certain range? I now I can set some properties while defining symbols, like positive=True, but I need more control, i....
- 1,755
19
votes
2
answers
41k
views
Using "from __future__ import division" in my program, but it isn't loaded with my program
I wrote the following program in Python 2 to do Newton's method computations for my math problem set, and while it works perfectly, for reasons unbeknownst to me, when I initially load it in ipython ...
- 193
19
votes
2
answers
2k
views
Representing rings of algebraic integers
I'm trying to represent the ring;
where theta is the root of a monic irreducible polynomial f with integer coefficients of degree d.
This ring is a subring of the algebraic integers, which itself ...
- 820
18
votes
3
answers
24k
views
Calculate curl of a vector field in Python and plot it with matplotlib
I need to calculate the curl of a vector field and plot it with matplotlib. A simple example of what I am looking for could be put like that:
How can I calculate and plot the curl of the vector field ...
- 311
18
votes
4
answers
3k
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How does sympy work? How does it interact with the interactive Python shell, and how does the interactive Python shell work?
What happens internally when I press Enter?
My motivation for asking, besides plain curiosity, is to figure out what happens when you
from sympy import *
and enter an expression. How does it go ...
- 665
18
votes
2
answers
16k
views
Convert sympy expressions to function of numpy arrays
I have a system of ODEs written in sympy:
from sympy.parsing.sympy_parser import parse_expr
xs = symbols('x1 x2')
ks = symbols('k1 k2')
strs = ['-k1 * x1**2 + k2 * x2', 'k1 * x1**2 - k2 * x2']
syms =...
- 8,938
18
votes
1
answer
6k
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Dealing with piecewise equations returned by sympy integrate
In sympy I have an integral which returns a Piecewise object, e.g.
In [2]: from sympy.abc import x,y,z
In [3]: test = exp(-x**2/z**2)
In [4]: itest = integrate(test,(x,0,oo))
In [5]: itest
Out[5]: ...
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17
votes
3
answers
26k
views
How to get the Gradient and Hessian | Sympy
Here is the situation: I have a symbolic function lamb which is function of the elements of the variable z and the functions elements of the variable h. Here is an image of the lamb symbolic function
...
- 775
17
votes
3
answers
71k
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No module named sympy
Hi I'm learning linear algebra with python with an Edx course. (http://nbviewer.ipython.org/github/ULAFF/notebooks/tree/may-14-2014/).
On "02.4.2.10 Practice with matrix-vector multiplication" with ...
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17
votes
5
answers
7k
views
Evaluating a mathematical expression (function) for a large number of input values fast
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 ...
- 3,493
17
votes
5
answers
3k
views
Evaluate inner product of bra and ket in Sympy Quantum
In sympy I have defined a two kets and a corresponding bra, when I apply the bra to the kets...
from sympy import sqrt
from sympy.physics.quantum import Bra,Ket,qapply
superpos = (Ket('Dead')+Ket('...
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16
votes
3
answers
5k
views
What does `S` signify in SymPy?
I am new to SymPy, and I can't figure out
from sympy.core import S
What is S actually? And what does S.true mean?
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15
votes
4
answers
4k
views
Display two Sympy plots as two Matplotlib subplots
This code
from sympy import *
x=Symbol('x')
p1 = plot(x**2,(x,-2,2))
p2 = plot(x**3,(x,-2,2))
results in two separate plots.
Instead of two separate plots, I want to display them with matplotlib ...
- 397
15
votes
2
answers
15k
views
Double integral with variable boundaries in python Scipy + sympy (?)
The full mathematical problem is here.
Briefly I want to integrate a function with a double integral. The inner integral has boundaries 20 and x-2, while the outer has boundaries 22 and 30.
I know ...
- 9,668
15
votes
2
answers
22k
views
From string to sympy expression
Recently I was working on a web application, using Flask and sympy libraries. The user enters his equation in a textarea and Flask rechieve it as a string. I would like to have the possibility to ...
- 821
15
votes
3
answers
9k
views
IPython Notebook Sympy Math Rendering
I have just started with using IPython Notebook and have been fascinated by its power. I have been using a few examples available on the net to get started with. I was following this tutorial: http://...
- 4,057
15
votes
1
answer
16k
views
Python Sympy Pretty Output of Matrix
Matrix([[607000, 907, 259, -2165, -1846, 185, -60, -1593, 1445, 1405], [-1000, -2, 0, -1, 0, 0, -1, 0, 0, -1], [0, 0, 1, 0, 0, 0, 0, 0, 0, 0], [-4000, -7, -3, 5, 4, 1, -1, 4, -4, -2], [-317000, -469, -...
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votes
1
answer
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Solving Systems of Equations with SymPy
I'm trying to solve a set of equations with SymPy 0.7.1:
from sympy import *
equations = [
Eq(S('vf'), S('vi + a*t')),
Eq(S('d'), S('vi*t + 1/2*a*t**2')),
Eq(S('a'), S('10')),
Eq(S('d'...
- 1,606
15
votes
1
answer
2k
views
sympy: order of result from solving a quadratic equation
I solved a quadratic equation using sympy:
import sympy as sp
q,qm,k,c0,c,vt,vm = sp.symbols('q qm k c0 c vt vm')
c = ( c0 * vt - q * vm) / vt
eq1 = sp.Eq(qm * k * c / (1 + k * c) ,q)
q_solve = sp....
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14
votes
6
answers
17k
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Ignore imaginary roots in sympy
I'm using sympy to solve a polynomial:
x = Symbol('x')
y = solve(int(row["scaleA"])*x**3 + int(row["scaleB"])*x**2 + int(row["scaleC"])*x + int(row["scaleD"]), x)
y is a list of possible solutions. ...
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14
votes
2
answers
16k
views
How to do a symbolic taylor expansion of an unknown function $f(x)$ using sympy
In sage it is fairly easy to do a Taylor expansion of an unknown function f(x),
x = var('x')
h = var('h')
f = function('f',x)
g1 = taylor(f,x,h,2)
How can this be done in sympy?
Update
asmeurer ...
- 9,496
14
votes
2
answers
828
views
Evaluate Irrational with Julia
Julia has the built-in constant pi, with type Irrational.
julia> pi
π = 3.1415926535897...
julia> π
π = 3.1415926535897...
julia> typeof(pi)
Irrational{:π}
Coming from SymPy, which has ...
- 3,481
14
votes
1
answer
17k
views
How to create vector of symbolic variables in sympy
How to create vector of symbolic variables in sympy? I want to do something like
x, x1, x2, x3 = symbols ('x x1 x2 x3')
A = [x+x1,x+x2,x+x3]
B = A * Transpose(A)
print (B)
A is array of symbolic ...
- 321
14
votes
2
answers
6k
views
Is there a vectorized way to calculate the gradient in sympy?
How does one calculate the (symbolic) gradient of a multivariate function in sympy?
Obviously I could calculate separately the derivative for each variable, but is there a vectorized operation that ...
- 7,707
14
votes
3
answers
5k
views
How to find all terms in an expression in Sympy
I have an expression as: 1/(x+1)+4*x/(x-1)+3-4*x**2+10*x**2
What I need is a list that contain the terms in this expression.
i.e. [1/(x+1), 4*x/(x-1), 3, -4*x**2 , 10*x**2]
update: It should not ...
- 2,421
14
votes
2
answers
8k
views
Factor/collect expression in Sympy
I have an equation like:
R₂⋅V₁ + R₃⋅V₁ - R₃⋅V₂
i₁ = ─────────────────────
R₁⋅R₂ + R₁⋅R₃ + R₂⋅R₃
defined and I'd like to split it into factors that include only single variable - in this ...
- 33.6k
14
votes
1
answer
2k
views
How to simplify matrix expressions in SymPy?
Consider the following example
import sympy as sy
n = sy.symbols('n')
A = sy.MatrixSymbol("A",n,n)
B = sy.MatrixSymbol("B",n,n)
C = sy.MatrixSymbol("C",n,n)
M = A.inverse()*B.inverse() - A.inverse()*...
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