How do I figure out what dependencies to install when I copy my Django app from one system to another?
On the source system execute pip freeze > requirements.txt, then copy the requiremnts.txt to the target system and then on the target system install all the dependencies with pip install -r requirements.txt.  Of course you will need to activate the virtual environments on both systems before execute the pip commands.
If you are using a source code management system like git it is a good idea to keep the requirements.txt up to date in your source code repository.
I'm using Django and Python 3.7.  I want to write a script to help me easily migrate my application from my local machien (a Mac High Sierra) to a CentOS Linux instance.  I'm using a virtual environment in both places.  There are many things that need to be done here, but to keep the question specific, how do I determine on my remote machine (where I'm deploying my project to), what dependencies are lacking?  I'm using rsync to copy the files (minus the virtual environment)