DEV Community: Hamdy Abou El Anein

Mastering Bash arguments with getopts

Hamdy Abou El Anein — Sun, 06 Mar 2022 10:48:34 +0000

In this article, I show you how to mastering the Bash arguments with getopts to have a software who run with professional arguments like
mysoft.bsh -f [arg1] -g [arg2]
I also show you how to add a default value if the argument is not given.

Here's an example of code :

f=10  
g=5  
while getopts ":f:g:" option; do  
    case "${option}" in  
        f)  
            f=${OPTARG}  
            ((f == 15 || f == 75)) || usage  
            ;;  
        g)  
            g=${OPTARG}  
            ;;  
        *)  
            usage
            ;;
    esac  
done  
shift $((OPTIND-1))  
if [ -z "${v}" ] || [ -z "${g}" ]; then  
    echo "info"  
fi  
echo "f = ${f}"  
echo "g = ${g}"

Now we can look at the code more closely :

Here we declare a default value to the variable -v and -g

f=10  
g=5

Here we use getopts with the arguments -f -g. If the user write, software.bsh -f value1 and/or -g value 2.

while getopts ":f:g:" option; do  
    case "${option}" in  
        f)  
            f=${OPTARG}  
            ((f == 15 || f == 75)) || usage  
            ;;  
        g)  
            g=${OPTARG}  
            ;;  
        *)  
            usage
            ;;
    esac  
done

That makes the arguments in Bash more professional.

Create a login page in Python with flask and/or gunicorn 💻 🐍

Hamdy Abou El Anein — Sat, 05 Feb 2022 18:59:48 +0000

In this post I will show you how to create a simple login page in Python with the flask library and finally with gunicorn.

let's begin!

Create the virtual env:

in the project directory :

python3 -m venv myenv

Then the linux command to activate the new env:
source /myenv/bin/activate

Now we are in our dev env.

From here install the flask library :

pip install flask

Now we can start to develop our flask app.

Create a file that you can call mylogin.py

In this file :

#!/usr/bin/env python3

from flask import Flask, render_template, redirect, url_for, request

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def login():
    error = None
    if request.method == 'POST':
        if request.form['username'] == 'Admin' and request.form['password'] == 'Admin1234$':
            return render_template("adminpage.html")
        elif request.form['username'] == 'User' and request.form['password'] == 'User1234$':
            return render_template("adminpage.html")
        else:
            return 'Invalid login or password, please try again'

    return render_template('login.html', error=error)


if __name__=='__main__':
    app.run(host='0.0.0.0')

We have created two users :

name: Admin
password : Admin1234$'

and

name: User
password: User1234$

mkdir templates

in templates, we will create 3 files :

adminpage.html login.html userpage.html

login.html

<html>
<head>
<title>Login page</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
    <div class="container">
        <h1>Please login</h1>
        <br>
        <form action="" method="post">
            <input type="text" placeholder="Username" name="username" value="{{  request.form.username }}">
            <input type="password" placeholder="Password" name="password" value="{{  request.form.password  }}">
            <input class="btn btn-default" type="submit" value="Login">
        </form>
        {% if error %}
            <p class="error"><strong>Error:</stong>  {{  error }}
        {% endif %}
    </div>
</body>
</html>

adminpage.html

<h1>This is the admin private page</h1>

userpage.html

<h1>>This is the user private page</h1>

Now you can test it with flask:

python mylogin.py

The app is running...

 * Serving Flask app 'mylogin' (lazy loading)
 * Environment: development
 * Debug mode: on
 * Running on all addresses.
   WARNING: This is a development server. Do not use it in a production deployment.
 * Running on http://YOUR.IP:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 521-493-757

Now open a web browser and connect to your ip : http://YOUR.IP:5000/

If you have a firewall installed, the port 5000 must be open.

You can now try to login with the admin the with the user account.

Now we can make it run for production with gunicorn :

install gunincorn:

pip install gunicorn

in the main directory, we need to create a file called :

wsgi.py

from mylogin import app

if __name__=='__main__':
    app.run()

Here mylogin is our mylogin.py Python/Flask app.

Now we can run it with gunicorn :

gunicorn --bind 0.0.0.0:5000 wsgi:app

It's running well...

[2022-02-05 19:51:48 +0100] [6545] [INFO] Starting gunicorn 20.1.0
[2022-02-05 19:51:48 +0100] [6545] [INFO] Listening at: http://0.0.0.0:5000 (6545)
[2022-02-05 19:51:48 +0100] [6545] [INFO] Using worker: sync
[2022-02-05 19:51:48 +0100] [6546] [INFO] Booting worker with pid: 6546

Open again your web browser at the same address and it's running.

The project directory is like this :

----Project-Directory-> | | --mylogin.py --wsgi.py | | ----Project-Directory->----templates-> | | --login.html --userpage.html --adminpage.html

Finally the library requirements in this project :

requirements.txt

click==8.0.3 Flask==2.0.2 gunicorn==20.1.0 itsdangerous==2.0.1 Jinja2==3.0.3 MarkupSafe==2.0.1 Werkzeug==2.0.2

How to find the N most present element in a list in Python 💻 🐍

Hamdy Abou El Anein — Wed, 26 Jan 2022 10:53:11 +0000

If you have a list in Python 🐍 and you need to find for example the 3 elements that are the must present in the list.

You can do it like this :

Create a list

mylist = [1,2,3,4,4,4,4,5,5,6,7,8,8,8,9]

Create two variables, maxcount is the number N of elements that we are searching.

count = 1
maxcount = 3

Use a while loop to find what we are looking for :

while count <= maxcount:
    num = max(set(mylist), key=mylist.count)
    print(num)
    count+=1
    while num in mylist:
        mylist.remove(num) #Here we remove the element that was the max

Now the full code:

mylist = [1,2,3,4,4,4,4,5,5,6,7,8,8,8,9]

count = 1
maxcount = 3

while count <= maxcount:
    num = max(set(mylist), key=mylist.count)
    print(num)
    count+=1
    while num in mylist:
        mylist.remove(num)

Now the result is :

4
8
5

You can even add them to a new list...