Please suggest me some apps or web sites to learn 3D animations.

Answer 1

Search Q&A for Blender, which is controlled by Python. I'll edit in one I posted in, because someone contributed an alternative with less of a steep learning curve.

edit: Recommendation for http://www.anim8or.com with an easier curve:
https://www.sololearn.com/Discuss/679531/?ref=app

Answer 2

Blender is for free (unique), Blender was entirely made with Python as Kirk said, and with Blender you can make 3D images, Animations, Motion Graphics, Movies and all your imagination could to create and your skills can construct. Blender is amazing !