'Returns the number of \'$\' characters right in front of s[i].'

def _count_dollars_before_index(self, s, i):

    dollar_count = 0
    dollar_index = (i - 1)
    while ((dollar_index > 0) and (s[dollar_index] == '$')):
        dollar_count += 1
        dollar_index -= 1
    return dollar_count
