Hello , How to get nikkei225 index all stock daily weighting by eikon with python API ? thank you.

Hi @ethan.hayashi

You can also do it directly, however please note that that
information is charged additionally as a part of ICW service (Index, Constituent and Weightings). You would need access to a service named Nikkei 225 Index with the exchange code NIX.
For more details, you can reach out to your Refinitiv representative.

ek.get_data("0#.FTSE","TR.IndexConstituentWeightPercent",{'Sdate':'2019-09-02'}