exponential.py 文件源码

def _eval_nseries(self, x, n, logx):
        # NOTE Please see the comment at the beginning of this file, labelled
        #      IMPORTANT.
        from sympy import limit, oo, Order, powsimp
        arg = self.args[0]
        arg_series = arg._eval_nseries(x, n=n, logx=logx)
        if arg_series.is_Order:
            return 1 + arg_series
        arg0 = limit(arg_series.removeO(), x, 0)
        if arg0 in [-oo, oo]:
            return self
        t = Dummy("t")
        exp_series = exp(t)._taylor(t, n)
        o = exp_series.getO()
        exp_series = exp_series.removeO()
        r = exp(arg0)*exp_series.subs(t, arg_series - arg0)
        r += Order(o.expr.subs(t, (arg_series - arg0)), x)
        r = r.expand()
        return powsimp(r, deep=True, combine='exp')