TypeError: no canonical coercion from <type 'NoneType'> to Callable function ring with argument N [closed]

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def eqDtm(eqn, nBelow, nAbove):#eqDtm is shortened for equilibrium determiner. eqn = f(N) if f(nBelow) >0 and f(nAbove) < 0: print "stable" elif f(nBelow) < 0 and f(nAbove) > 0: print "unstable" elif f(nBelow) > 0 and f(nAbove) > 0: print "semistable" elif f(nBelow) < 0 and f(nAbove) < 0: print "semistable" else: print "Not an equilibrium point" ---------- from random import uniform def randomGen(num,num2): uniform(num, num2) ---------- var("r,N,A,K") r= 0.1 A= 5. K= 100 eqn = (rN(1-(N/K))*((N/A)-1)) Eq = [0, 5, 100] for value in Eq: if value == max(Eq): eqDtm(eqn, randomGen(Eq[1],Eq[2]),randomGen(Eq[2],Eq[2]+1)) print "maximum equilibirum point" elif value == min(Eq): eqDtm(eqn, randomGen(Eq[0]-1, Eq[0]),randomGen(Eq[0],Eq[1])) print "minimum equilibirum point" else: eqDtm(eqn, randomGen(Eq[0],Eq[1]),randomGen(Eq[1],Eq[2])) print "neither"

I don't understand the error that's specified in the title. Can anyone explain this?