Question

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 possible solution, but my gut tells me that it’s not going to be very efficient. Please let me know if there is a better way of doing this.

I’m new to SymPy and am still feeling my way about. As far as I can see, Symbols need to be defined with a string. Therefore, I can produce a series strings via appending an incrementing number to a letter (say ‘t0’, ‘t1’, etc), add them to a list and then create the symbols using those strings as parameters. Those symbols would themselves be stored in a list and would be used to produce the equations.

def solveEquations(numEquations):
    symbolNameList = []
    symbolList = []
    equationList = []
    for i in range(numEquations):
        name = 't' + str(i)
        symbolNameList.append(name)
        symbolList.append(Symbol(name))

    for i in range(numEquations):
        equation = 0
        for sym in symbolList:
            equation += sym ** i # Or whatever structure the equation needs
        equationList.append(equation)


    #Then go on to solve the equations...

Is this the best way of doing this, or is there a more efficient approach?

Answer 1

The symbols function can be used to easily generate lists of symbols

In [1]: symbols('a0:3')
Out[1]: (a₀, a₁, a₂)

In [2]: numEquations = 15

In [3]: symbols('a0:%d'%numEquations)
Out[3]: (a₀, a₁, a₂, a₃, a₄, a₅, a₆, a₇, a₈, a₉, a₁₀, a₁₁, a₁₂, a₁₃, a₁₄)