import pymongo causes `ImportError: cannot import name BSON`. how do you fix the import error?

Try uninstalling the bson and pymongo packages and then reinstalling the pymongo package. pymongo installs its own bson package and I think you've overwritten it with the other bson package installation and that is probably what is causing your import error.

FYI:

• when you pip install pymongo it also installs bson but it does not ever print a message saying that it is install bson to your virtualenv site-packages
• also pymongo does not list bson as a dep
• also pip -v list does not show that bson is installed
• those bullet points IMO have some code smell (at least print a message stating you are installing bson)

I met the same problem.I think the reason is I install pymongo and then install bson.Then I uninstall bson. Then I got this problem.

pip freeze pymongo it requires Nothing.

So maybe it has its own bson package.

What I solve this problem:

pip uninstall pymongo

pip uninstall bson

and then reinstall pymongo

pip install pymongo

You are returning a list in hello(). You need to return a string or a Response object, see Flask docs. E.g. convert the list to a string before returning:

return '\n'.join(json_docs)