Running OpenSSL command in Python subprocess

Question

I am trying to run an OpenSSL decrypt command via Python's subprocess module, but have no luck so far:

import subprocess

check = subprocess.run('openssl enc -aes-256-cbc -d -in filepath_in -out filepath_out -K aes_key -iv iv_key', capture_output=True, text=True, shell=True).stdout
print(check)

The script returns nothing. However, when running the same string in the command line manually - everything works and it returns an output. Substituting the string with something simple like 'help' does print a proper cmd output, meaning the following code works without issues:

import subprocess

check = subprocess.run('help', capture_output=True, text=True, shell=True).stdout
print(check)

My goal is to run an OpenSSL command via subprocess and capture the output. Would greatly appreciate any tips/pointers.