Why am I getting an empty list as my output using solve command?
<p>I am trying to solve an equation using sympy's solve command but my output is an empty list [ ]. The only reason I think this could be happening is because there is no solution but I doubt that is the reason. Anyone know why I am not getting an answer? Thanks!</p>

<pre><code>from sympy import *

class WaterModel:

    def fp_requirement(self, Ws0, Wp0, Wg0):
        greyW = 60.0
        potW = 126.0
        rainW = 17.05

        self.Ws0 = Ws0
        self.Wp0 = Wp0
        self.Wg0 = Wg0

        self.fp = var('fp')

        filt_greyW = self.fp*greyW
        dWg = self.Wg0 - greyW + (1 - self.fp)*greyW + rainW
        dWp = self.Wp0 - potW + filt_greyW 
        F = self.Ws0 + dWp + dWg
        self.fp = solve(F,self.fp)

        return self.fp 

a = WaterModel()
fp = a.fp_requirement(1500, 100, 100)
print(fp)
</code></pre>

<p><code>self.fp</code> cancels out of your computation. The value of <code>F</code> is the same no matter what <code>self.fp</code> is, so <code>solve</code> can't help you.</p>

<p>Are you sure you have your equations right?</p>

python sympy solver is-empty