I was wanting to use some non-standard python packages in my project and was wondering how to add them. What is the benefit of using the AWS eb config files (.ebextensions and requirements.txt) rather than just downloading and including the package in my actual project under a lib directory like you would with a java application?
by including it in the requirements.txt, you can include only the packages you are calling.  Pip then takes care of installing the dependencies and checking the versions.
This has the additional advantage of when you are changing or upgrading your project, you can specify a new version of the library you are using and all the dependent libraries will also be updated.
Adding external packages to elastic beanstalk python app