what is the best way to import high frequency updating data in python?
Since there is no code and I don't know the website, here are some general thoughts:

As Maxime suggested - Is there an API you could use?
Can you ditch selenium? Using something like requests might be faster and will help you get the timings right.
Is the stuff you want to scrape already loaded when you try to save it?
Is your internet connection keeping up with the amount of requests you sent?
I am trying to import some data from web, where the data is being updated every 1 second. 
However, the problem is that when I try to soup this data, all data are not imported. When the data is not being updated, my code works well. But when the data is being updated(from 8 a.m. to 12 a.m.), some of those are not imported properly. 
It's a table with 500 rows and 12 columns, where each column is stored in a separate variable. It is expected that the variables have the same length. This is true when data are not updated, but when I run the code from 8 a.m. to 12 a.m.(when data are being updated) the variables do not have the same length. Any advice or recommendation would be greatly appreciated.
I am using selenium to open the web page and execute some commands to read data with beautiful-soup.