Hi Soumil,
I assume you are sending data from Python to MATALB via TCP/IP connection. The TCP/IP receive block used in the simulink model has a parameter called 'Block Sample Time'. You can specify the block sample time which is the rate at which block is executed during the simulation.
The other thing I could think of is about the Blocking Mode property of the block. This is enabled by default. If it is enabled, it will block the simulation until data is received.
To receive the data continuously without blocking the simulation, disable the blocking mode.
Hope the above information helps you.