Develop Reference

Trying to run a python file in flask

I am trying to learn flask. I created a venv and installed flask. I set the flaskblog.py as FLASK_APP. But it says serving flask app 'app.py' and it fails. why is this?
I'm not sure if the image is visible. So, I'll write what I've tried below,
In the windows powershell, I cd to the directory where my venv and python script is, then
$ . vnev\Scripts\activate
$ pip install flask
$ set FLASK_APP=flaskblog.py
$ flask run
it gives me the error saying,
Serving Flask app 'app.py' (lazy loading)
Environment: production
WARNING: This is a development server. Do not use it in a production deployment.
Use a production WSGI server instead.
Debug mode: off
Usage: flask run [OPTIONS]
Try 'flask run --help' for help.
Error: Could not import 'app'.
What is wrong here? I have also tried $ setx FLASK_APP "flaskblog.py and still get the same result. I think i created this app.py using pycharm's virtual environment and now, I cannot set other files to FLASK_APP.
What should I do?

How to hot reload grpc-server in python?

I'm developing some python microservices with grpc and i'm using docker for the cassandra database and the microservices. Is there a way to setup reload on change within docker-compose?
I'm guessing that first I need the code mounted as a volume but I don't see a way to reload on GRPC server like for example flask does.

We use watchdog[watchmedo] with our grpc services and Docker.
Install watchdog or add to your requirements.txt file
python -m pip install watchdog[watchmedo]
Then in your docker-compose.yml add watchmedo auto-restart --recursive --pattern="*.py" --directory="/usr/src/app/" python -- -m app to your container where --directory is the directory to where your app is contained inside the docker container, and python -- -m app is the file that starts your grpc Server. In this example the file that starts the server is called app.py:
app:
build:
context: ./app/
dockerfile: ./Dockerfile
target: app
command: watchmedo auto-restart --recursive --pattern="*.py" --directory="/usr/src/app/" python -- -m app
volumes:
- ./app/:/usr/src/app/

Docker: How do I debug localhost "Internal Server Error"?

First time using Docker(version 19.03.5) and trying this tutorial
I'm stuck on step 2.3.4 Running an image
When I go to http://localhost:8888 I see
Internal Server Error
The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.
I updated Dockerfile to this to match my directory:
# our base image
FROM alpine:3.5
# Install python and pip
RUN apk add --update py2-pip
# install Python modules needed by the Python app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
# copy files required for the app to run
COPY app.py .
COPY templates/index.html templates
# tell the port number the container should expose
EXPOSE 5000
# run the application
CMD ["python", "app.py"]
On my command line I have
C:\Users\user\docker\flask-app>docker run -p 8888:5000 --name flask-app 11111111/flask-app
* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
When I visit the page I see on the prompt
172.17.0.1 - - [05/Jan/2020 07:14:34] "GET / HTTP/1.1" 500 -
I have this in my app.py
from flask import Flask, render_template
import random
app = Flask(__name__)
# list of cat images
images = [
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr05/15/9/anigif_enhanced-buzz-26388-1381844103-11.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr01/15/9/anigif_enhanced-buzz-31540-1381844535-8.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr05/15/9/anigif_enhanced-buzz-26390-1381844163-18.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr06/15/10/anigif_enhanced-buzz-1376-1381846217-0.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr03/15/9/anigif_enhanced-buzz-3391-1381844336-26.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr06/15/10/anigif_enhanced-buzz-29111-1381845968-0.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr03/15/9/anigif_enhanced-buzz-3409-1381844582-13.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr02/15/9/anigif_enhanced-buzz-19667-1381844937-10.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr05/15/9/anigif_enhanced-buzz-26358-1381845043-13.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr06/15/9/anigif_enhanced-buzz-18774-1381844645-6.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr06/15/9/anigif_enhanced-buzz-25158-1381844793-0.gif",
"http://img.buzzfeed.com/buzzfeed-static/static/2013-10/enhanced/webdr03/15/10/anigif_enhanced-buzz-11980-1381846269-1.gif"
]
#app.route('/')
def index():
url = random.choice(images)
return render_template('index.html', url=url)
if __name__ == "__main__":
app.run(host="0.0.0.0")
I can't figure out why my page isnt loading. Any help would be appreciated.
Note: I have WAMP installed and this might be conflicting but not sure if thats the case and/or how to fix it.

Flask might be unable to locate your templates. Try changing
COPY templates/index.html templates
to
COPY templates templates
to copy everything inside ./templates to <WORKDIR>/templates.
Using COPY templates/index.html templates will copy index.html as a file at path <WORKDIR>/templates, not copy it under that directory.

How to debug your Flask application in Docker:
Turn on Flask debugger by adding ENV FLASK_DEBUG=1 to your Dockerfile
Try to run the Flask app outside of Docker. It may be easier to set breakpoints inside your IDE (VSCode or PyCharm) and debug the app.
Try pdb to debug the app inside the container. It may be hard for a beginner, but in general, it's an essential skill. Check Debugging a Python Flask Application in a Docker Container for a step-by-step guide.

Note: This is more aimed at the question "How do I debug". It was unclear that the OP actually wanted a solution, not a way to solve the problem.
First thing to do is to start the container without the app in it. For that, you replace the CMD ["python", "app.py"] with CMD ["sleep", "inf"]. Now, after starting the container, you can get a shell in the container using docker exec -it flask-app /bin/bash to get a shell. In the shell, you can then use the regular Python debugger to set a breakpoint in the / handler and then single-step through the code to track down what Python's doing.

Unable to load python flask API with a docker container

I'm trying to learn Docker containers with APIs. I have created a simple Hello World python REST API with flask:
from flask import Flask
app = Flask(__name__)
#app.route("/")
def hello():
return "Hello World!"
if __name__ == '__main__':
app.run(host="127.0.0.1", debug=True, port=8080)
This works when I run the script and go to http://localhost:8080/
This is my Dockerfile:
# Use an official Python runtime as a parent image
FROM python:2.7-slim
# Set the working directory to /app
WORKDIR /hello_world
# Copy the current directory contents into the container at /app
ADD . /hello_world
# Install any needed packages specified in requirements.txt
RUN pip install --trusted-host pypi.python.org -r requirements.txt
EXPOSE 8080
# Define environment variable
ENV NAME World
# Run app.py when the container launches
CMD ["python", "hello_world.py"]
requirements.txt:
Flask
My current directory contains Dockerfile, hello_world.py and requirements.txt.
I can successfully build the image with docker build -t hello_world ."
Running it with docker run -p 8080:8080 -t hello_world gives me the following output:
Serving Flask app "hello_world" (lazy loading)
* Environment: production
WARNING: Do not use the development server in a production environment.
Use a production WSGI server instead.
* Debug mode: on
* Running on http://127.0.0.1:8080/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: 985-433-141
When I try going to http://127.0.0.1:8080/ I get the "Can't reach this page" error. Do you know what I'm doing wrong? Thank you.

GAE ERROR :- /bin/sh: 1: exec: gunicorn: not found

I trying to deploy my app on GAE using their trial version. I was so far successful in creating an app.yaml with a custom settings for flexible environment with python 3.6.
However, while deploying the app, the app builds successfully, however, I keep getting the following error
Updating service [default] (this may take several minutes)...failed.
ERROR: (gcloud.app.deploy) Error Response: [9]
Application startup error:
/bin/sh: 1: exec: gunicorn: not found
Following is the folder hierarchy of files in my project:
Following the code for app.yaml
env: flex
runtime: custom
api_version: 1
entrypoint: gunicorn -b :$PORT main:app
runtime_config:
python_version: 3.6
#handlers:
#- url: /SmsResponse
# script: Twilio_Routing.RecivedSms
#
#- url: /CallResponse
# script: Twilio_Routing.ReceivedCall
I am surely missing out on something and I would really appreciate some help here.
Link to git repo
requirements.txt
Flask==0.10.1
gunicorn==19.3.0
twilio==6.8.4
DockerFile
FROM gcr.io/google-appengine/python
LABEL python_version=python3.6
RUN virtualenv --no-download /env -p python3.6
# Set virtualenv environment variables. This is equivalent to running
# source /env/bin/activate
ENV VIRTUAL_ENV /env
ENV PATH /env/bin:$PATH
# Copy the application's requirements.txt and run pip to install all
# dependencies into the virtualenv.
ADD requirements.txt requirements.txt
RUN pip install -r requirements.txt
ADD . /app/
#CMD gunicorn -b :$PORT main:app
ENTRYPOINT [ "python", "Twilio_Routing.py" ]
P.S. After the changes for the requirements.txt, I am getting error 502 Bad Gateway.
Logs showing that the service was executed successfully.
017-12-25 01:29:03 default[20171224t212610] * Running on http://127.0.0.1:8080/ (Press CTRL+C to quit)
2017-12-25 01:29:03 default[20171224t212610] * Restarting with stat
2017-12-25 01:29:03 default[20171224t212610] * Debugger is active!
2017-12-25 01:29:03 default[20171224t212610] * Debugger PIN: 134-103-452
2017-12-25 01:29:17 default[20171224t212610] * Running on http://127.0.0.1:8080/ (Press CTRL+C to quit)
2017-12-25 01:29:17 default[20171224t212610] * Restarting with stat
2017-12-25 01:29:17 default[20171224t212610] * Debugger is active!
2017-12-25 01:29:17 default[20171224t212610] * Debugger PIN: 134-103-452
Can someone look at my code in git and tell me what is it that I am missing here?

for me the error was as simple as making sure gunicorn was in requirements.txt
Flask==1.0.2
gunicorn==19.9.0
Note:
I see the OP had added this flag; this is to help others that may be running into exec: gunicorn: not found

A few changes and I was able to run your app in docker.
In Twilio_Routing.py , change host to listen on 0.0.0.0 instead of 127.0.0.1.This is needed to to have the server available externally as well.
Since your app.yaml is already configured, you don't need to customize your Dockerfile as Google App Engine requires. Keep it as your own custom one.Here's what I used:
#Python's Alpine Base Image
FROM python:3.6-alpine3.6
#Installing all python modules specified
ADD requirements.txt requirements.txt
RUN pip install -r requirements.txt
#Copy App Contents
ADD . /app
WORKDIR /app
#Start Flask Server
CMD [ "python","Twilio_Routing.py"]
#Expose server port
EXPOSE 8080

Considering the example shown in the GoogleCloudPlatform/python-runtime page, consider changing your CMD line from:
CMD exec gunicorn -b :$PORT main:app
To:
CMD gunicorn -b :$PORT main:app
I see exec used here only when the base image is the python one, not gcr.io/google-appengine/python.

I also came across this error recently when I tried to run my docker image.
/bin/sh: 1: gunicorn: not found
Simple trick that worked for me
delete the container and the image
restart the docker engine.
and try to create the image again using the below commands
docker build -t <image_name>:<tag_name> .
and try to run using this command.
docker run -p 5000:5000 -e PORT =5000 image id
it worked for me! hope it helps.