Python subprocess error: Popen, call, run "No such file or directory: error

I'm having issues with the subprocess module. I'm trying to run a terminal command in Python, which works perfectly fine in the terminal. The command is:

hrun SomeAction LogFile

I've tried a variety of options, including call(), run(), check_output(), and Popen(). No matter which method I use, I get the error:

FileNotFoundError: [Errno 2] No such file or directory: 'hrun': 'hrun'

My code is:

    output = Popen(["hrun", "SomeAction", log_file_name], stdout=PIPE, stderr=PIPE)

where "hrun" and "SomeAction" are strings and log_file_name is a string variable. I found other SO issues and, most (if not all) were resolved with either shell=True (which I dont want), or because the issue was due to a string instead of a list argument.

Thanks!

#python