MS adduct masses calculator

mz.py

class Mz(object):
    
    def __init__(self, mz, z = 1, sign = None, tolerance = 0.01):
        self.mz = mz
        self.z = z
        self.sign = sign
        self.tol = tolerance
    
    def __eq__(self, other):
        return self.z == other.z and \
            self.mz > other.mz - self.tol and \
            self.mz < other.mz + self.tol
    
    def __str__(self):
        return 'm/z = %f' % self.mz
    
    def adduct(self, m):
        return (self.mz * self.z + float(m)) / abs(self.z)
    
    def weight(self):
        return self.mz * self.z
    
    def remove_h(self):
        return self.adduct(-mass.proton)
    
    def remove_ac(self):
        m = MolWeight('H3C2O2')
        return self.adduct(-m - mass.electron)
    
    def remove_fo(self):
        m = MolWeight('HCO2')
        return self.adduct(-m - mass.electron)
    
    def remove_nh4(self):
        m = MolWeight('NH4')
        return self.adduct(-m + mass.electron)
    
    def remove_oh(self):
        m = MolWeight('OH')
        return self.adduct(-m - mass.electron)
    
    def add_h(self):
        return self.adduct(mass.proton)
    
    def add_2h(self):
        return self.adduct(2 * mass.proton)
    
    def add_3h(self):
        return self.adduct(3 * mass.proton)
    
    def add_oh(self):
        m = MolWeight('OH')
        return self.adduct(m + mass.electron)
    
    def add_fo(self):
        m = MolWeight('HCO2')
        return self.adduct(m + mass.electron)
    
    def add_ac(self):
        m = MolWeight('H3C2O2')
        return self.adduct(m + mass.electron)
    
    def add_nh4(self):
        m = MolWeight('NH4')
        return self.adduct(m - mass.electron)
    
    def add_na(self):
        m = MolWeight('Na')
        return self.adduct(m - mass.electron)
    
    def remove_na(self):
        m = MolWeight('Na')
        return self.adduct(-m + mass.electron)
    
    def reload(self):
        modname = self.__class__.__module__
        mod = __import__(modname, fromlist = [modname.split('.')[0]])
        reload(mod)
        new = getattr(mod, self.__class__.__name__)
        setattr(self, '__class__', new)