class BayesNet:

    def __init__(self, ldep=None):
        if not ldep:
            ldep = {}
        self.dependencies = ldep

    def add(self,var,mothers,prob):
        self.dependencies.setdefault(var,{})[frozenset(mothers)] = prob

    def jointProb(self,conjunction):
        prob = 1.0
        for (var,val) in conjunction:
            for (mothers,p) in self.dependencies[var].items():
                if mothers.issubset(conjunction):
                    prob*=(p if val else 1-p)
        return prob