No Sympy two-sided limits?

问题

I can't get Sympy to handle two-sided limits. Running in a Jupyter notebook, Anaconda installation:

from sympy import *
x = symbols('x')
limit(1/x,x,0)

gives an answer of oo. Furthermore,

Limit(1/x,x,0)

prints as a right-sided limit. In fact, all of my two-sided limits 'pretty-print' as right-sided limits. They seem to be evaluated that way, too. Can't find a way to force two-sided. Of course, one could write a short program to remedy this.

What am I doing wrong?

回答1:

limit has a fourth argument, dir, which specifies a direction:

>>> limit(1/x, x, 0, '+')
oo
>>> limit(1/x, x, 0, '-')
-oo
>>> limit(1/x, x, 0)
oo

The default is from the right. Bidirectional limits are not directly implemented yet, but you can easily check both directions.

回答2:

Two sided limits are now directly implemented.

>>> limit(1/x**2, x, 0, '+-')
oo

来源：https://stackoverflow.com/questions/39672198/no-sympy-two-sided-limits