flask-example/app.py

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

# Create the application.
APP = Flask(__name__)

# Define different routes of the application.
@APP.route('/', methods=['GET', 'POST'])
def index():

	title = "Hello Flask"

	# If something is submitted through the form...
	# ref: https://pythonbasics.org/flask-http-methods/
	if request.method == 'POST':

		# Read the values from the form element.
		name = request.form['name']
		text = request.form['text']

		# Write the submitted data to a file, which is
		# in this case a "csv" (comma seperated values) file
		# that you can also open with spreadsheet software.
		# Note that the file is opened in the mode "a+"
		# which means that the Flask application will append values
		# (and not overwrite the csv file).
		with open('database.csv', 'a+') as db:
			db.write(f"{ name},{ text }\n")

		msg = "Thanks!"
		# PRG pattern(Post Redirect Get pattern), to avoid repetition of contents
		# https://en.wikipedia.org/wiki/Post/Redirect/Get
		return redirect(url_for('index'))
	
	# If the index page is loaded...
	else:
		msg = "Please submite the form below."
		return render_template('index.html', title=title, msg=msg)

if __name__ == '__main__':
	APP.debug = True
	APP.run(port = 3000)