A couple possibilities occur to me:

1. A Potential Path Problem

Your python command might refer to a different python than the python which is in your active conda environment folder. Check this by running in terminal which conda and which python. If you get something like the below, you’re good here.

/anaconda3/bin/conda
/anaconda3/envs/<yourEnvName>/bin/python

If you are getting different paths, it is possible your path is messed up. open up your .bashrc file and double check lines associated with python and conda.

Alternatively, reinstall conda.

2. A Very Vexing Version Variation

You might have a version/dependency incompatibility issue. This seems unlikely to me as visdom is compatible with python 2.7 onward (I think) and you clearly are using python 3.5.2. Nonetheless, this might happen if you are using multiple package managers. Nowadays it is less common, but it does happen occasionally. Try checking this by running pip show visdom and/or conda search --reverse-dependency visdom or the equivalent for your package manager.

If this is indeed a problem, then I suggest first updating your packages and if that does not work then uninstalling visdom with the original package manager and trying to install with a different package manager.

If all of the above fails, start exploring your problem from a new environment. Can you replicate it in the new environment? (I can’t). Can you replicate it on another machine? etc…

Keep the internets updated with your problem as we might be able to help some others out!