python pex to distribute a project

I have a python project and want to distribute it as a single file. I found PEX but found it difficult to use. Initially, I thought if my project is in a folder like the following

<folder>\
    project.py
    submodule1
        file1.py
        file2.py
    submodule2
        file3.py
        ...

When cd into the folder and do python project.py, it run fine. I then want to put it into a single file for distribution. I found PEX and watched "WTF is PEX". I understand the theory of PEX but unable to build a single pex file so that when I execute the file, it is the same as "python project.py"

I try

pex -r requirement.txt -o x.pex
pex -r requirement.txt -c whatever ...
pex -r requirement.txt -e whatever ...

None of the above work, because PEX will only create a virtualenv with all the required module installed, the projects sources were not packaged into the .pex file.

In order to put my project sources into PEX, I need to package it. So I created a setup.py and try

pex . -o x.pex

Then no matter how I try, I still cannot run the program. I try -c and -e switch, none of them work.

If PEX is designed to zip all the sources along with a python virtualenv (along with all the required modules), is there a simple way that

pex -r requirement project.py -o x.pex

which will build a pex file, package the project sources along with the virtualenv, and run as if "python project.py"? Or there is a way except I don't know how to use pex.

Can any one help, thanks.