CODEWITHSUNDEEP
pythonparsinglinear-algebrasympysolver
Björn Johansson
Björn Johansson

Reputation: 406

Solving set of linear equations in plaintext using sympy

I would like to add a functionality to solve systems of linear equations to my python based editor. I am looking for a module that would be able to parse a string such as the one below:

sample_volume=20
final_concentration=0.55
ethanol_concentration=0.96

final_volume = ethanol_vol+sample_volume
final_concentration*final_volume=ethanol_vol*ethanol_concentration

And solve for the values of all variables.

I have implemented a quick and dirty script using sympy that does this, see here for a Jupyter notebook.

I think that this must have been implemented by someone in a more robust way, I would like to avoid reinventing the wheel here.

Does anyone know of any alternative implementation that are more robust (have tests etc)?

Additionally, according to the sympy docs, sympy.solveset should be used instead of sympy.solve. I cannot make this work with a list of equations as in my example. Can someone proficient in sympy guide me how to use solveset with an equation system such as this.

Upvotes: 1

Views: 311

Answers (1)

Shekhar Prasad Rajak
Shekhar Prasad Rajak

Reputation: 304

In [2]: sample_volume=20
   ...: final_concentration=0.55
   ...: ethanol_concentration=0.96
   ...: 

In [4]: fv,ev = symbols('fv,ev')

In [5]: expr1 = fv - ev+sample_volume

In [6]: expr2 = final_concentration*fv - ev*ethanol_concentration 

In [7]: solve([expr1,expr2], [fv,ev])
Out[7]: {ev: -26.8292682926829, fv: -46.8292682926829}

# I will recommend to use solveset's linear system solver (linsolve)
In [8]: linsolve([expr1,expr2], [fv,ev])
Out[8]: {(-46.8292682926829, -26.8292682926829)}

Upvotes: 2

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