Determine how to create the present participle from the root word

PresentParticiple

class Participle:
    def __init__(self, ending):
        self.vowels = ['a', 'e', 'i', 'o', 'u']
        self.doublingConsonants = ['b', 'd', 'g', 'k', 'l', 'm', 'n', 
                                   'p', 'r', 't', 'v', 'z']
        self.vvgExceptions = {
                              'abhor': 'abhorring',
                              'aver': 'averring',
                              'ballot': 'balloting',
                              'babysit': 'babysitting',
                              'baby-sit': 'baby-sitting',
                              'buffet': 'buffeting',
                              'carol': 'caroling',
                              'discomfit' : 'discomfiting',
                              'excel': 'excelling',
                              'fillet': 'filleting',
                              'fret': 'fretting',
                              'gas': 'gassing',
                              'glom': 'glomming',
                              'grit': 'gritting',
                              'mortar': 'mortaring',
                              'murmur': 'murmuring',
                              'nom': 'nomming',
                              'parrot': 'parroting',
                              'pen': 'penning',
                              'pivot': 'pivoting',
                              'pilfer': 'pilfering',
                              'profit': 'profiting',
                              'rebel': 'rebelling',
                              'regret':'regretting',
                              'rival': 'rivaling',
                              'segue': 'segueing',
                              'singe': 'singeing',
                              'surveil': 'surveilling',
                              'target': 'targeting',
                              'vomit': 'vomiting',
                              'whet': 'whetting'
                              }

        self.vvgPipeline = [self._vvgExceptions,
                            self._addK,
                            self._qDoubleVowel,
                            self._doubleVowel,
                            self._fer,
                            self._pel,
                            self._noDoublingCheckLast2,
                            self._noDoublingCheckLast3,
                            self._noDoublingCheckLast4,
                            self._noDoublingCheckLast5,
                            self._doubleConsonant,
                            self._dropIEaddY,
                            self._dropE,
                            self._default]
        self.ending = 'ing'

    def _addK(self, w0):
        if w0[-2:] in ['ac', 'ic']:
            return w0 + 'k' + self.ending

    def _default(self, w0):
        return w0 + self.ending

    def _doubleConsonant(self, w0):
        if len(w0) > 1 and w0[-2] in self.vowels and w0[-1] in self.doublingConsonants:
            root = w0[:-1]
            double = w0[-1]
            return root + double + double + self.ending

    def _doubleVowel(self, w0):
        if len(w0) > 2 and w0[-3] in self.vowels and w0[-2] in self.vowels:
            return w0 + self.ending

    def _dropE(self, w0):
        if len(w0) > 1 and w0[-1] == 'e' and w0[-2] not in ['e', 'o']:
            return w0[:-1] + self.ending

    def _dropIEaddY(self, w0):
        if w0[-2:] == 'ie':
            return w0[:-2] + 'y' + self.ending

    def _fer(self, w0):
        if w0[-3:] == 'fer' and w0[-4:] != 'ffer':
            return w0 + 'r' + self.ending

    def _noDoublingCheckLast2(self, w0):
        if w0[-2:] in ['er', 'el', 'en', 'om', 'on', 'or']:
            return w0 + self.ending

    def _noDoublingCheckLast3(self, w0):
        ''' 
        check for length greater than 3 because 'pet' and 'vet' double, 
        but not 'carpet' and 'rivet'
        '''
        if len(w0) > 3 and w0[-3:] in ['bit', 'cil', 'cit', 'dit', 'gar', 
                                       'het', 'ket', 'lar', 'met', 'pet', 
                                       'ret', 'ril', 'rit', 'sit', 'vet', 
                                       'vil', 'xit']:
            return w0 + self.ending

    def _noDoublingCheckLast4(self, w0):
        if w0[-4:] in ['dget', 'elop', 'llop']:
            return w0 + self.ending

    def _noDoublingCheckLast5(self, w0):
        if w0[-5:] in ['limit', 'pilot']:
            return w0 + self.ending

    def _pel(self, w0):
        if w0[-3:] == 'pel':
            return w0 + 'l' + self.ending

    def _qDoubleVowel(self, w0):
        ''' squat, acquit, quiz, quit, equip
            but not equal and conquer
        '''
        if w0[-4:] in ['qual', 'quer']:
            return None

        if (len(w0) > 3 and w0[-4] == 'q' 
            and w0[-3] in self.vowels and w0[-2] in self.vowels
            and w0[-1] in self.doublingConsonants):
            root = w0[:-1]
            double = w0[-1]
            return root + double + double + self.ending

    def _vvgExceptions(self, w0):
        if w0 in self.vvgExceptions:
            return self.vvgExceptions[w0]

    def toParticiple(self, w0):
        for fn in self.vvgPipeline:
            vvg = fn(w0)
            if vvg: 
                return vvg