Hi@Gaurav,
You can use set_index function in pandas. It allows you to set an index according to your requirement. You can use this below code.
import pandas as pd
df= pd.DataFrame({"Day":[1,2,3,4], "Visitors":[200, 100,230,300], "Bounce_Rate":[20,45,60,10]}) 
df.set_index("Day", inplace= True)
 | 
 | 
| Day | 
visitors  | 
Bounce_Rate | 
| 1 | 
200 | 
20 | 
| 2 | 
100 | 
45 | 
| 3 | 
230 | 
60 | 
| 4 | 
300 | 
10 |