List dependencies in Python

Question

What is the most efficient way to list all dependencies required to deploy a working project elsewhere (on a different OS, say)?

Python 2.7, Windows dev environment, not using a virtualenv per project, but a global dev environment, installing libraries as needed, happily hopping from one project to the next.

I've kept track of most (not sure all) libraries I had to install for a given project. I have not kept track of any sub-dependencies that came auto-installed with them. Doing pip freeze lists both, plus all the other libraries that were ever installed.

Is there a way to list what you need to install, no more, no less, to deploy the project?

EDIT In view of the answers below, some clarification. My project consists of a bunch of modules (that I wrote), each with a bunch of imports. Should I just copy-paste all the imports from all modules into a single file, sort eliminating duplicates, and throw out all from the standard library (and how do I know they are)? Or is there a better way? That's the question.

Answer 1

pipreqs solves the problem. It generates project-level requirement.txt file.

Install pipreqs: pip install pipreqs

1. Generate project-level requirement.txt file: pipreqs /path/to/your/project/
2. requirements file would be saved in /path/to/your/project/requirements.txt

If you want to read more advantages of pipreqs over pip freeze, read it from here