gistfile1.txt

I was following this one..
https://docs.docker.com/get-started/part2/#introduction
=============================================
Dockerfile

# Use an official  python runtime as a parent image.
FROM python:2.7-slim

# set the working directory to /app
WORKDIR /app

# copy everything from the current folder to app.
COPY . /app

# install all the dependencies mentioned in the requirements txt.
RUN pip install --trusted-host pypi.python.org -r requirements.txt

# expose the port 80
EXPOSE 80

#defined the environment name as world.
ENV NAME world

# run the app.py when the container launches
CMD [ "python", "app.py" ]

# Set proxy server, replace host:port with values for your servers
ENV http_proxy host:port
ENV https_proxy host:port

===========================================
requirements.txt
Flask
Redis
 ===========================================
python.py

from flask import flask
from redis import Redis, RedisError
import os
import socket

redis = Redis(host="redis", db=0, socket_connect_timeout=2, socket_timeout=2)

app = Flask(__name__)

@app.route("/")

def thello44():
    try:
        visits = redis.incr("counter")
    except RedisError:
        visits = "<i>cannot connect to Redis, counter disabled</i>"

    html = "Hello from herer"

    return html;

if __name__ == "__main__"
    app.run(host='0.0.0.0', port=80)
    
    ============================================
    everytime i run 
docker run -p 4000:80 hellopython
i am getting issue saying 

  File "app.py", line 11
    def hello()
              ^
SyntaxError: invalid syntax

things i have tried.
1) delete all containers.
2) restart docker.

what i didnot understand was.
while i am trying to "docker run -p 4000:80 hellopython" its loading from old file instead of newly created method.
notice the name of the method.its showing error in