IsADirectoryError: [Errno 21] Is a directory: '/app' when deploying on Heroku - flask

Question

I've been having trouble deploying my Flask app on Heroku. My current problem is Heroku can't locate the files in my static folder. After trying suggestions on SO, I am now getting this error:
with open(file_dir, encoding="utf-8") as f:
IsADirectoryError: [Errno 21] Is a directory: '/app'
Here's one of the suggestions I found to help Heroku find the encouragement.txt file:
# Absolute path to the file
file_dir = os.path.dirname(os.path.abspath('encouragement.txt'))
# Absolute path to this file's root directory
parent_dir = os.path.join(file_dir, os.pardir)
app_dir = os.path.join(parent_dir, '/app')
The '/app' was added because one of the posts mentioned that Heroku had an app directory as the parent directory, so instead of 'static/encouragement.txt', it would be 'app/static/encouragement.txt'. The same error was given with and without joining '/app'.
Here's where the error came from:
#app.route("/")
def index():
# Read data from the file as str
with open(file_dir, encoding="utf-8") as f:
messages = f.read()
I tried using heroku bash command to check the file system structure and confirm the app directory but the command executed and returned blank.
My files are organized as follow:
MyProject
> static
> encouragement.txt
app.py
Not sure if it's needed, but I'm using windows. Thank you.
Update:
I tried adding index.php and composer.json as a couple tutorials suggested. They didn't work for the txt files; not sure if they helped with the other static files though. Not the best solution, but I ended up just copying and pasting all the txt content to my app.py.

Answer 1

I ran into this issue today after doing a bit of "clean-up" to my environment variables/configs. The issue is you're trying to open a directory itself as if it were a file, which causes the error. I recommend the answer in this article (as shown).
import os
# path to your file
file_name = r'/app/static/encouragement.txt'
print(os.path.isfile(file_name))
with open(file_name, 'r', encoding='utf-8') as f:
lines = f.readlines()
print(lines)