From what I have learnt in the documentation it states that you can easily switch between 2 python environments by just creating a new variable using command prompt
"conda create -n python34 python=3.4 anaconda" if i already have python 2.7 installed.
An environment named python 34 is created and we can activate it using "activate python 34" But all this happens like executing the above commands happens in my windows command prompt. I want to switch between python versions in spyder IDE, How to do this?
Spyder is launched from the environment that you're using.
So if you want to use python 3 in Spyder then you activate python34 (or whatever you named the environment with Python 3) then run spyder.
If you want to use python 2 in Spyder then you deactivate the python3 environment (or activate an environment in which you installed Python 2) then run spyder.
I do not believe that you can change environments once Spyder is launched.
N.B. you may need to install Spyder in each environment, depending on your set up, by first activating the environment then using conda install spyder.
Just go to the directory where you have installed Spyder(use cd in command prompt), for me, it looks like "C:\Users\Rohan\Anaconda2" and type spyder in cmd. it will run your Spyder IDE.
来源：https://stackoverflow.com/questions/42788383/switch-between-spyder-for-python-2-and-3