This exif_tool.py is a command line tool meant to quickly list EXIF creation date and time stamps (also referred to as
an image file's origin time stamp).  I created this so I could batch modify tens (or more) image files with a single
command. Applications like Photos.app on macOS make use of the EXIF origin date to sort photos and the 'touch -t'
command doesn't do anything to the EXIF datetime stamp unless the file already has it.

Requirements:
Python3.6+ (tested 3.6.10)

Install/Setup:
There's no real install since it's just a Python script, however there is one add-on Python module needed and the script
is written and tested in Python 3.7.  The required module is listed in the 'requirements.txt' file which can be
installed using the standard Python tool 'pip' or more specifically 'pip3' with Python version 3.x.  It's best to make
use of virtual Python environments rather than installing modules into the system level Python locations.  I used
'virtualenv' but other virtual environment managers should work just fine (as would installing modules into the system
level Python interpreter).  Virtual environments can eliminate conflicts between versions of system level modules or
libraries, and you can easily create, delete, and recreate virtual environments.  This is par for the course for most
Python savvy folks.  I also use PyCharm as my Python IDE which can build virtual environments without the need for
installing 'virtualenv'.  If you don't want to install a Python IDE just to create quick virtual environments for
Python, it can be setup at a user-level as follows (i.e. no need to install as root or an administrator).

Setup with 'virtualenv':

pip3 install virtualenv --user

You might get a message that says virtualenv is not in the system path. This is easy enough to add to either the
~/.bash_profile or ~/.bashrc file (depending on what platform you're on).  For macOS 12.14.x, pip3 tells me  it
installed 'virtualenv' into '/Users/<username>/Library/Python/3.7/bin' and that I should add this to my users path.  On
macOS (vs Linux) the terminal app reads ~/.bash_profile, so I add the following to the '.bash_profile' file in my user
home directory.

export PATH="$PATH:~/Library/Python/3.7/bin"

On macOS, restart a new terminal window and 'virtualenv' becomes available.  You can then create a virtual environment
with required modules as follows (I'm using /Users/<username>/env3 as the location of my virtual env):

virtualenv -p python3.7 ~/venv

To make the new Python3.7 environment active within the current terminal (so you can continue installing from the
included 'requirements.txt' file), source the 'activate' file as follows:

source ~/venv/bin/activate

On macOS 12.14.6, the system only has pip3 by default, but 'virtualenv' creates environments that contain both 'pip'
and 'pip3' (it doesn't matter which you use in that case).  The following command reads all modules listed in
'requirements.txt' and installs it within the Python interpreter installed in '~/venv'.

pip3 install -r requirements.txt

If you want to execute the 'exif_tool.py' you can either type (while the virtual env is active):

python exif_tool.py -h

Or you can change the very first line of the 'exif_tool.py' file to the location of the virtual env interpreter you just
installed and setup.

Example:
My username happens to be 'esteban' and the home directory '/Users/esteban' so the first line of 'exif_tool.py' when
pulled from git reads '#!/Users/esteban/venv/bin/python' because that is literally where my virtualenv interpreter
resides. So just substitute you username inplace of 'esteban' and the tool will execute without needing to
'source ~/venv/bin/activate' each time you want to execute the python program/script.  If the script file has execute
permissions, then typing in the name of the script prefixed by it's path should work (assume we all know './' below
means 'exif_tool.py' is in the current working directory):

./exif_tool.py -h

usage: exif_tool.py [-h] [-t SET] [-l] [file [file ...]]

Set or list the EXIF creation date and time on image files.

positional arguments:
  file               file_name or file_name_pattern

optional arguments:
  -h, --help         show this help message and exit
  -t SET, --set SET  integer datetime formatted: [[CC]YY]mmddHHMM.[SS]
  -l, --list         list EXIF dates if they exist


If you don't put the 'exif_tool.py' in a folder included in the PATH, you'll always need to type the fully qualified
path to the program.

Lastly, you can deactivate the virtual python environment by typing 'deactivate' which returns your terminal window to
the normal system version of Python.