def get_prev_char_pos(self, i=None):
        if self.pos == 0: return 0
        if i is None: i = -1
        return self.tokens[i][0]
Get the previous position (one token back) in the input text.
dataset/ETHPy150Open kuri65536/python-for-android/python-modules/twisted/twisted/words/xish/xpathparser.py/Scanner.get_prev_char_pos