query strings and request object

 To list all properties/methods of an object, use dir function.

inst = ClassA()

dir(inst) ##to list all properties/methods of object

We can read a dictonary object elements using get method.

##reading dictionaries:

r = ('greeting': 'hello')

type(r) # dict

r.get('greeting')

Similarly, the REQUEST data sent from client browser, will be received as REQUEST object and its contents are acessed using the python get method.

How data is passed by client.

www.abc.com/?greeting=hello

part after / is the query string.

And the key/value pairs are parameters

REQUST object:

1. context variable

2. holds the GET request details

3. python dictionary with key-value pairs

localhost:5000/new/?greeting=hello

The above data is passed using REQUEST object to below code.

from flask import Flask, request, render_template

app = Flask(__name__)

@app.route('/index')

@app.route('/')

def hello_flask():

  return 'Hello flask!'

@app.route('/new/')

def query_strings(greeting):

  query_val = request.args.get('greeting')

  return '<h1> the greeting is : {0} </h1>'.format(query_val)

if __name__ == '__main__':

  app.run(debug=True)

The REQUEST object is accessed using request in flask library imported.

We can set a default value in the python code so that if user didn't pass data, we can use the default value.

from flask import Flask, request, render_template

app = Flask(__name__)

@app.route('/index')

@app.route('/')

def hello_flask():

  return 'Hello flask!'

@app.route('/new/')

def query_strings(greeting = 'default_value'):

  query_val = request.args.get('greeting', greeting) # second arg is optional to pass default value

  return '<h1> the greeting is : {0} </h1>'.format(query_val)

if __name__ == '__main__':

  app.run(debug=True)

we can use variables in query url itself instead of passing query strings.

@app.route('/user')

@app.route('/user/name')

def no_query_strings(name='mina'):

  return '<h1>hello there! {}</h1>'.format(name)

The url to test:

localhost:5000/user/testuser