Tried to import 'plotly' but failed

Expected behavior

Plot of param importances of optimized study.

Environment

• Optuna version: 2.9.1
• Python version: 3.8.5
• OS: Windows 10
• Plotly: 5.3.1

Error messages, stack traces, or logs

ImportError: Tried to import 'plotly' but failed. Please make sure that the package is installed correctly to use this feature. Actual error: No module named 'plotly'.
---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
~\Anaconda3\lib\site-packages\optuna\visualization\_plotly_imports.py in <module>
      6 with try_import() as _imports:  # NOQA
----> 7     import plotly  # NOQA
      8     from plotly import __version__ as plotly_version

ModuleNotFoundError: No module named 'plotly'

The above exception was the direct cause of the following exception:

ImportError                               Traceback (most recent call last)
<ipython-input-46-ec7b157c78f5> in <module>
----> 1 optuna.visualization.plot_param_importances(study)

~\Anaconda3\lib\site-packages\optuna\visualization\_param_importances.py in plot_param_importances(study, evaluator, params, target, target_name)
     93     """
     94 
---> 95     _imports.check()
     96     _check_plot_args(study, target, target_name)
     97 

~\Anaconda3\lib\site-packages\optuna\_imports.py in check(self)
     84         if self._deferred is not None:
     85             exc_value, message = self._deferred
---> 86             raise ImportError(message) from exc_value
     87 
     88 

ImportError: Tried to import 'plotly' but failed. Please make sure that the package is installed correctly to use this feature. Actual error: No module named 'plotly'.

Steps to reproduce

1. Create objective, optimize study
2. Run optuna.visualization.plot_param_importances(study)

Additional context (optional)

This issue here https://github.com/optuna/optuna/issues/1339 has been closed but others have continued reporting similar issues.

[muzitache]

I still have same issue after reinstall plotly with conda. Importing plotly and checking version works well with import plotly and plotly.__version__

so I have been applying these fixes but didn’t work, turns out i needed to restart my system. This fixed my issue.

[cj2001]

Bump!

Same problem here…