def EvalPoissonPmf(k, lam):
 return (((lam ** k) * math.exp((- lam))) / special.gamma((k + 1)))

def EvalPoissonPmf ( k , lam ) : return ( ( ( lam ** k ) * math . exp ( ( - lam ) ) ) / special . gamma ( ( k + 1 ) ) )
computes the poisson pmf .