list python package dependencies without loading them?

Snakefood

sfood -fuq package.py | sfood-target-files 

will list the dependencies.

`-f` tells sfood to follow dependencies recursively
`-u` tells sfood to ignore unused imports
`-q` tells sfood to be quiet about debugging information

To filter out modules from the standard library, you could use

sfood -fuq package.py | sfood-filter-stdlib | sfood-target-files 

As you've already noted, if there are other directories you'd like ignored, you can also use the sfood -I flag.

modulefinder from the standard lib

New in version 2.3.

This module provides a ModuleFinder class that can be used to determine the set of modules imported by a script. modulefinder.py can also be run as a script, giving the filename of a Python script as its argument, after which a report of the imported modules will be printed.

I am not sure if it complies with your requierement about not loading the modules. From here:

modulefinder use bytecode inspection to find dependencies, and therefore is free from any side-effects that may be caused by importing the modules being studied.

Other hints about the use of pylint or Gui2exe here

If by package you mean a pip installed package (and not a directory with an __init__.py), then you can use the Python package called pip. For example:

def get_all_package_dependencies():
    """Return dictionary of installed packages to list of package dependencies."""
    return {
        dist.key: [r.key for r in dist.requires()]
        for dist in pip.get_installed_distributions()
    }