First Step of the Stemmer.

stemming.py

    def _porter_step_1(self, word):
        """
        Deals with plurals and past participles.

        """
        stem = word
        stepb2 = False
        #Step 1a
        if stem.endswith('sses'):
            stem = stem[:-2]
        elif stem.endswith('ies'):
            stem = stem[:-2]
        elif not stem.endswith('ss') and stem.endswith("s"):
            stem = stem[:-1]
        #Step 1b
        if len(stem) > 4:
            if stem.endswith("eed") and self._det_m(stem) > 0:
                stem = stem[:-1]
            elif stem.endswith("ed"):
                stem = stem[:-2]
                if not self._chk_v(stem):
                    stem = word
                else:
                    stepb2 = True
            elif stem.endswith("ing"):
                stem = stem[:-3]
                if not self._chk_v(stem):
                    stem = word
                else:
                    stepb2 = True
                    #Step 1b.2
        if stepb2:
            if stem.endswith("at") or stem.endswith("bl") or stem.endswith("iz"):
                stem += "e"
            elif self._chk_d(stem) and not (self._chk_LT(stem,"lsz")):
                stem = stem[:-1]
            elif self._det_m(stem)==1 and self._chk_o(stem):
                stem += "e"
        #Step 1c
        if self._chk_v(stem) and stem.endswith('y'):
            stem = stem[:-1]+'i'
        return stem