Pandas Package import is not reinforced

[ashwinsnambiar]

Expected behavior

While trying to use the study.trials_dataframe() functions, pandas dataframe object is returned. But since the setup.py doesn't have a requirement to install panda package, it causes an error. In optuna.study._dataframe.py file, there is a check to try importing pandas if available. There is no exception cause here. Should pandas be set as a requirement?

Environment

• Optuna version:3.5.0
• Python version:3.10.13
• OS:Linux-5.15.0-94-generic-x86_64-with-glibc2.31
• (Optional) Other libraries and their versions:

Error messages, stack traces, or logs

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

Steps to reproduce

1.Run any study

# python code
study.trials_dataframe().to_csv("study_results.csv")

Additional context (optional)

No response

[nzw0301]

pandas is an optional package as defined in

optuna/pyproject.toml

Lines 83 to 95 in d132cd9

	optional = [
	"boto3", # optuna/artifacts/_boto3.py.
	"cmaes>=0.10.0", # optuna/samplers/_cmaes.py.
	"google-cloud-storage", # optuna/artifacts/_gcs.py.
	"matplotlib!=3.6.0", # optuna/visualization/matplotlib.
	"pandas", # optuna/study.py.
	"plotly>=4.9.0", # optuna/visualization.
	"redis", # optuna/storages/redis.py.
	"scikit-learn>=0.24.2",
	# optuna/visualization/param_importances.py.
	"scipy", # optuna/samplers/_gp
	"torch", # optuna/samplers/_gp
	]

.