====== Работа с формами из Flask ======
<code python>
from flask import Flask, request
from flask import abort, redirect, url_for


#app = Flask('app')
app = Flask(__name__)

@app.route('/')
def hello_world():
  return """Hello, World!
    <a href="/exit?page=8&filter=18&required=abc">Test</a>
    <form method="POST" action="/form">
    <input type="text" name="name">
    <input type="text" name="surname">
    <input type="submit">
    </form>"""

@app.route('/exit', methods=['GET'])
def exit_world():
  page = request.args.get('page', default = 1, type = int)
  filter = request.args.get('filter', default = '*', type = str)
  required = request.args['required']
  return("Exit Page " + str(page) + ", filter=" + filter + " req=" + required)

@app.route('/form', methods=['POST'])
def formTest():
  if request.method == 'POST':
    name = request.form['name']
    surname = request.form.get('surname')
    if surname == None:
      surname = ""
    return '<h1>Hello '+name+' '+surname+'</h1><a href="/">back</a>'
  else:
    hello_world()

@app.route("/json_post")
def json_test():
  # {"language":"Python","primary":{"version":3.8},"arr":[1,2,3]}
  json = request.get_json()
  lang = json["language"]
  version = json["primary"]["version"]
  # arr1 = json["arr"][0]
  nonrequiredValue = None
  if 'nonrequiredValue' in json:
    nonrequiredValue['nonrequiredValue']
  return "Language {} and version {}" % (lang, version)

@app.route('/')
def index():
    return redirect(url_for('login'))

@app.route('/login')
def login():
    abort(401)
    return "this_is_never_executed"


@app.errorhandler(404)
def page_not_found(error):
    return render_template('page_not_found.html'), 404

if __name__ == '__main__':
  app.run(host='0.0.0.0', port=8080, debug=None)
</code>