Deepika Padukone has stepped into period drama genre with "Bajirao Mastani", but Sanjay Leela Bhansali's historical love saga is turning out to be an arduous task for the actress. She says the film is "physically, mentally and emotionally draining".

"The film is definitely the toughest of my career. The film has been extremely draining, be it physically, mentally or emotionally. The nature of the movie and the director is very demanding," Deepika said at the film's song launch here.

The track titled "Deewani Mastani" was launched at Day One of Blenders Pride Fashion Tour 2015 here on Saturday.

The actress has teamed up with Bhansali for the second time -- "Goliyon Ki Rasleela Ram-Leela" was the first.

"Bajirao Mastani" narrates the love story of Maratha Peshwa Bajirao I (played by Ranveer Singh) and his second wife Mastani (Deepika). Actress Priyanka Chopra plays Bajirao's first wife Kashibai. The film is scheduled to release on December 18.

For Deepika, the push by the director helps an actor push the envelope and get better in the craft.

"He (Bhansali) is never happy with what he sees. He is very clear about what he wants from his actors and team. So, he pushes you and helps you discover something within yourself that you didn't know existed," the actress said.

"He is a hard task master. You learn so much about yourself. It has been the most difficult experience, but in the end you feel it is worth it," she added.

After making a name for herself in the world of modelling, Deepika entered Bollywood with "Om Shanti Om" in 2007, and went on to take Hindi filmdom with a storm.

She has been appreciated by one and all for experimenting with different storylines like "Piku", "Aarakshan" and "Finding Fanny". Her line-up of upcoming movies is also quite impressive like "Tamasha" apart from "Bajirao Mastani".