Simple application in Python using OpenCV for face
Some notes only:

Instead of

(_, im) = webcam.read()


is more common not to use parentheses:

_, im = webcam.read()


(and similarly in other places of your code).



Too many blank lines. In the PEP 8 - Style Guide for Python Code repeatedly occurs the word "sparingly" for the Blank Lines usage.



(Correcting English only):

Instead of

print("Webcam is open? ", webcam.isOpened())


use

print("Is the webcam open? ", webcam.isOpened())




Magic numbers in your code, as in this statement

if key == 27:


Why not use names for such constants, e. g.

ESC_KEY = 27               # Near the start of your code
...
...
if key == ESC_KEY: