ModuleNotFoundError: No module named 'flask_session'

Question

I have a simple python file that I am trying to set up to utilize sessions, when i run the file I am receiving the error below:

ModuleNotFoundError: No module named 'flask_session'

I believe I am importing the module properly, is there anything else that I can check to set this up properly?

from flask import Flask, render_template, request, session
from flask_session import Session

app = Flask(__name__)

app.config["SESSION_PERMANENT"] = False
app.config["SESSION_TYPE"] = "filesystem"

Session(app)

@app.route("/", methods=["GET", "POST"])
def index():
    if session.get("notes") is None:
        session["notes"] = []

    if request.method == "POST":
        note = request.form.get("note")
        session["notes"].append(note)

    return render_template("index.html", notes=notes)

Here is the traceback ( most recent call last )

File "c:\python37\lib\site-packages\flask\cli.py", line 325, in __call__
Open an interactive python shell in this frameself._flush_bg_loading_exception()

File "c:\python37\lib\site-packages\flask\cli.py", line 313, in _flush_bg_loading_exception
reraise(*exc_info)

File "c:\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
raise value

File "c:\python37\lib\site-packages\flask\cli.py", line 302, in _load_app
self._load_unlocked()

File "c:\python37\lib\site-packages\flask\cli.py", line 317, in _load_unlocked
self._app = rv = self.loader()

File "c:\python37\lib\site-packages\flask\cli.py", line 372, in load_app
app = locate_app(self, import_name, name)

File "c:\python37\lib\site-packages\flask\cli.py", line 242, in locate_app
'\n\n{tb}'.format(name=module_name, tb=traceback.format_exc())

Answer 1

I've first encountered this problem while doing Harvard's CS50x class. I'm using Linux and I've been using Python3, as it turns out I've installed Flask-Session for Python2. I don't know whether it also applies to Mac but I used the following instead:

$ pip3 install flask-session

Then you can check whether it's installed with pip's freeze command. After doing this my pylint in VSCode no longer gave an error.