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Running flask command via crontab

I have a simple script that executes a flask command called sendemail (located in the "main" blueprint).
The "task" script, located in /home/ubuntu/tasks:
cd /home/ubuntu/app
source venv/bin/activate
flask main sendemail
deactivate
When I run (from anywhere, including the home directory)
bash /home/ubuntu/tasks/task
The function runs exactly as intended. However, when I add this same script to crontab, it produces an error, emailing me this message:
/home/ubuntu/tasks/task: line 4: flask: command not found
I've made sure that I have the latest flask installed and assume this might have something to do with the PATH variables - how can I fix/debug this?

The activation doesn’t work in the cron because you don’t have the same environment variables. You can use set > /path/to/your.log to diagnose…
You can simplify your scrip by calling Flask directly:
/home/ubuntu/app/venv/bin/flask main sendemail

Problem with flask using Python 3.7.6 with vscode on mac

I have a weird problem with some code I want to run. The code itself should not be the problem since it is downloaded from a Udemy class and not modified:
# coding=utf-8
from flask import Flask, render_template, request
app = Flask(__name__)
#app.route("/")
def hello():
items = ["Apfel", "Birne", "Banane"]
return render_template("start.html", name="Max Mustermann", items=items)
#app.route("/test")
def test():
name = request.args.get("name")
return render_template("test.html", name=name)
I found online that, to start the emulated webserver(?) I have to rund the following temrinal commands before I can see the output:
(base) Christophs-MBP:13-23 chris$ export FLASK_APP=run.py run flask
(base) Christophs-MBP:13-23 chris$ export FLASK_APP=run.py run flask
(base) Christophs-MBP:13-23 chris$ export FLASK_APP=run.py
(base) Christophs-MBP:13-23 chris$ run flask
bash: run: command not found
No reaction to my terminal commands
Basically there is no reaction to the command to start the server(?).It should reply with "Running on 127.0.0.1:5000" as soon as I've run the command once.
If I go to my browser, there is no page when I address http://127.0.0.1:5000. What am I doing wrong? I am pretty new to Python and an absolute rookie regarding the terminal. Not sure if I broke something there, since trying to install pyenv to manage my Python installs better as recommended by a friend does not work either (I cannot update the SDK headers as described on RealPython

What are the export statements?
On Mac, export key=value creates a new (or updates an existing one) environment variable - the tutorial most likely simply asked you to provide one where key is FLASK_APP and value is a path to your app.
To verify it's been saved correctly, you can list the variables by just typing export in the terminal and finding out what's inside each of the environment variables on your system (if you want to only view FLASK_APP you can type export | grep FLASK_APP).
Why do you need FLASK_APP?
When you call flask run in your terminal, you will see the following message:
Error: Could not locate a Flask application. You did not provide the "FLASK_APP" environment variable, and a "wsgi.py" or "app.py"
module was not found in the current directory.
I presume your file is called run.py, therefore none of the conditions are met. You could rename run.py to app.py and simply type flask run in the terminal, but you can also type export FLASK_APP=<path-to-run.py>. It seems the tutorial author decided to do the latter. Keep in mind that if you rename your file to app.py you will need to run flask run within the directory that file lives in. You can change directory in the terminal using cd command.
Why do you get bash: run: command not found?
bash is a language running inside your terminal, and it only knows of a few commands - it is not aware of any run commands. It does however know about flask command once you have installed it on your machine. Within the command's output there is a part which includes a run command:
Commands:
routes Show the routes for the app.
run Run a development server.
shell Run a shell in the app context.
Therefore, what you want to do is type flask run instead of just run in your terminal.

Django - pass commands to shell

I have an django project on Heroku and I need to update the DB daily. Manually i would open manage.py shell and write there this:
from app import views
views.function()
One way i found to do that automatic is through a heroku scheduler, however I would like to know if it is possible to tell the shell what commands should it run.
I was doing this:
python -c "from app import views;views.function"
but it gives me an error because that should be done on the shell instead of the command line, so is it possible to tell the shell what should it write?
Thanks :D

You can write a custom django command, something like my_command.py and call it from the command line:
python manage.py my_command
https://docs.djangoproject.com/en/1.11/howto/custom-management-commands/

How to script django shell operations?

I'd like to create a script (.sh or python, not important) that can do the following:
heroku pg:reset DATABASE_URL
heroku run python manage.py migrate
heroku run python manage.py shell
> from myapp.scenarios import *; reset_demo_data(); exit()
Line 1 to 3 are UNIX commands, but Line 4 is python to be executed in the opened Django shell.
I tried stuff with | and > to "inject" the python code in the command but nothing worked.
I guess it's quite easy to do but I can't figure out how..
Thanks.

I guess the best option would be to write a custom management command.
Your script could then look like:
heroku pg:reset DATABASE_URL
heroku run python manage.py migrate
heroku run python manage.py shell
heroku run python manage.py reset_demo
when the management command is something like:
from django.core.management.base import BaseCommand
from myapp.scenarios import *
class Command(BaseCommand):
def handle(self, *args, **options):
reset_demo_data()

Or you can try this one line solution:
echo "from myapp.scenarios import *; reset_demo_data(); exit()" | python manage.py shell
You can add this line replacing Shell activation line.

Auto restart django development server on file save after previous error

While writing the code, I usually am in the habit of saving the file every minute or so. Sometimes, that leads to situations where the function is not complete, and I have saved it, causing the django development server to throw up an error like following:
Unhandled exception in thread started by ...
Traceback
..
..
File "/home/user/work/project/api/file.py", line 26
def update_something(self, )
^
SyntaxError: invalid syntax
Now in cases when the code is working fine, the django dev server auto-restarts on file save with reflected changes. How can I make the django server recover from the failed Error state and restart the server automatically on subsequent file saves?
Currently, I have to stop the python manage.py runserver command in terminal, and run it manually again.
I am using django 1.5.3 on python 2.7.6

I use a simple bash script for this. Here's a one-liner you can use:
$ while true; do python manage.py runserver; sleep 2; done
That will wait 2 seconds before attempting to restart the server. Insert whatever you think is a sane value.
I usually write this as a shell script named runserver.sh, put it in my project root (the same directory with manage.py in it) and add it to the gitignore.
while true; do
echo "Re-starting Django runserver"
python manage.py runserver
sleep 2
done
If you do this, remember to chmod +x runserver.sh, then you can execute it with:
./runserver.sh
Use Ctrl-c Ctrl-c to exit.

On windows you may use a batch file, write this as a batch script named runserver.bat
#echo off
setlocal EnableDelayedExpansion
setlocal EnableExtensions
:WHILE_0
if 1 EQU 1 (
python manage.py runserver
sleep 2
goto WHILE_0
)
Then you can execute it clicking it or from the command line:
./runserver.sh