I currently planning for build a stock trading app using react for study purpose. Is there is any api that can give realtime stock price data and if you can please suggest me a good charting package for my project.
As your question is vague, it all depends on what you want to achieve. From my experience in working in wealth management, you will not find a reliable API and especially realtime for free.
If you're making a PoC, you might want to use EOD data which is usually available for free.
If you really need reliable realtime data, you might want to have a look at :
The lists written above are not exhaustive and i have no interest in any of those API's listed. Just run a proper google search and I am sure you will find what fits you.
Beside, concerning the data visualisation library your tags mention django and reactjs. It is not very clear if you want to display data from a ui framework or from django directly. Therefore I will list what I know the most :
Hope my answer will give you some lights.